<reasoning_content>
Thinking Process:

1.  **Analyze the Request:**
    *   Goal: Implement a basic job queue in Python.
    *   Class Name: `JobQueue`.
    *   Methods:
        *   `add_job(job_id: str, data: dict) -> str`: Add job, return job_id.
        *   `get_result(job_id: str) -> dict | None`: Get result of completed job.
    *   Constraints:
        *   FIFO order.
        *   Store jobs internally until processed.
        *   Unique job_id (input provided in the method signature, but the method returns it).
    *   Output: Python code only, no explanations.

2.  **Determine Internal State:**
    *   Need a way to store pending jobs (queue structure). A `deque` is ideal for FIFO.
    *   Need a way to store results of completed jobs. A dictionary mapping `job_id` to `result` is appropriate.
    *   Need a way to track job status (pending, completed). The `data` dict could potentially hold status, or a separate status dict. Let's keep it simple: store jobs in a queue and results in a separate dictionary.
    *   Wait, the prompt says "The queue should store jobs internally until they are processed". This implies there's a processing mechanism implied, but the class itself doesn't necessarily need a background thread unless specified. However, to make `get_result` work as described in the example ("After processing..."), there needs to be a mechanism to mark jobs as completed.
    *   Since the prompt asks for a "basic job queue" implementation, usually this implies the structure to manage jobs. But without an external worker, how does a job get processed?
    *   Interpretation 1: The class manages the queue, but the user must manually trigger processing or the class simulates processing.
    *   Interpretation 2: The class manages the queue and provides a way to retrieve the job to process it, then mark it done.
    *   Interpretation 3: The class simulates processing immediately.
    *   Let's look at the example usage:
        ```python
        job_id = queue.add_job("job1", {"task": "process_data"})
        # After processing...
        result = queue.get_result("job1")
        ```
        This suggests `add_job` queues it. `get_result` retrieves the result. The processing logic is implicit or external.
        To make this functional within the class definition:
        1.  `add_job` stores the job in a queue (list/deque) and a results dict.
        2.  `get_result` checks the results dict.
        3.  We need a method to simulate/perform the processing so that `get_result` returns something other than `None` after a job is done. Or, we assume the user will update the status.
        4.  However, a standard "Job Queue" implementation usually involves a worker or a `process` method.
        5.  Given the minimal requirements, I should probably implement a `process` method or assume the user updates the internal state.
        6.  Let's look at the requirements again. "The queue should store jobs internally until they are processed".
        7.  To make `get_result` useful, the class needs a way to know when a job is done.
        8.  Simplest approach for a "basic" implementation without external threading:
            *   Store pending jobs in a `deque`.
            *   Store completed jobs in a `dict`.
            *   Add a `process()` method (or similar) that pops from the queue and saves to the results dict.
            *   Or, just implement the storage logic and assume the user handles the "processing" part via an external system, but `get_result` needs to access stored results.
            *   Better approach: Implement a `process_job` method or just handle the queueing logic and allow retrieving the job.
            *   Actually, looking at the signature `get_result(job_id: str) -> dict | None`, it implies the result is stored.
            *   Let's add a `process_all` or similar mechanism to make it testable, or just store the job data and allow the user to mark it complete.
            *   Let's stick to the strictest interpretation of the provided methods first.
            *   `add_job`: Adds to a queue.
            *   `get_result`: Returns from a results cache.
            *   To make it work, I need to simulate processing. Let's add a `process` method that pops from the queue and adds to the results.

    *   Refined Plan:
        1.  `__init__`: Initialize `queue` (deque) and `results` (dict).
        2.  `add_job`: Validate ID, store data in queue, return ID.
        3.  `process`: (Optional but helpful) Pop from queue, store in results. Or allow manual status update.
        4.  `get_result`: Check results dict.

    *   Wait, the prompt doesn't explicitly ask for a `process` method, but without it, `get_result` will always return `None` unless I simulate processing inside `add_job`.
    *   If I simulate processing inside `add_job`, it's not a queue, it's just a map.
    *   If I require a `process` method, it makes the queue functional.
    *   Let's check if I can infer processing. "The queue should store jobs internally until they are processed". This implies there is a state of "not processed".
    *   I will add a `process` method to the class to make it functional, or I will assume the user calls a method to advance the queue.
    *   Actually, to keep it strictly to the requested methods (`add_job`, `get_result`), maybe the processing happens asynchronously?
    *   Let's implement a simple `process` method to trigger the "processing" state change so `get_result` works in the example context. Or, I can implement `get_result` to check if the job is in the queue (pending) vs results (completed).
    *   Let's add a `process` method to the class to ensure the example usage makes sense (i.e., the job actually gets processed).
    *   Actually, I can implement `get_result` to return `None` if not found, and `add_job` to store the job. The example says "After processing...". I should probably implement a `process` method that moves items from the queue to the results dict so the example works.
    *   Wait, strict adherence to requirements: "Create a `JobQueue` class with the following methods: ...". It lists `add_job` and `get_result`. It doesn't explicitly forbid other methods, but implies these are the interface.
    *   To make the example work ("After processing..."), I need a way to mark a job as processed.
    *   I will add a `process` method (or `process_all`) to move jobs from queue to results.
    *   Wait, if I add a method not listed, is it okay? Usually yes, as long as the listed ones work.
    *   Let's try to do it with just the two methods if possible.
    *   Maybe `add_job` returns a job object? No, it returns `job_id`.
    *   Maybe `get_result` triggers processing? No, that's weird.
    *   Okay, I will implement a `process` method to make it a valid queue implementation, as a queue needs a way to dequeue/process.
    *   Wait, strictly speaking, a queue just holds data. The "processing" is the consumer.
    *   Let's assume the user implements the processing loop externally.
    *   However, for the code to be runnable and demonstrate the logic, I should include a mechanism.
    *   Let's implement a `process` method that takes no arguments and processes the head of the queue.
    *   Actually, let's look at the constraint: "Write only the Python code".
    *   I will implement the class with `add_job`, `get_result`, and a helper `process_job` or `process` method to make it functional, or I'll store a status in the data.
    *   Let's store the job data in a dict `self.jobs` and a queue `self.queue`.
    *   To keep it simple and robust:
        1.  `__init__`: `self.queue = deque()`, `self.results = {}`.
        2.  `add_job`: `self.queue.append({'id': job_id, 'data': data})`, return `job_id`.
        3.  `get_result`: Return `self.results.get(job_id)`.
        4.  To make `get_result` return something after "processing", I need to simulate processing. I'll add a `process` method.

    *   Wait, looking at the prompt requirements again:
        "Create a `JobQueue` class with the following methods: `add_job`... `get_result`..."
        It doesn't say "only these methods".
        So adding `process` is acceptable to satisfy the "stored until processed" logic.

    *   Wait, I can also just store the job in a dict keyed by ID, and have a status field.
    *   But FIFO is required. So a queue structure is needed for pending jobs.
    *   Let's implement `process` method to pop from queue and save to results.

    *   Wait, one more check: The example usage shows `job_id = queue.add_job(...)`.
    *   If I don't provide a way to trigger processing, `get_result` will always return None.
    *   I will include a `process` method.

    *   Wait, I should check if I can interpret `get_result` as fetching the data if not processed? No, it says "result of a completed job".
    *   Okay, I'll add a `process` method.

    *   Wait, I need to make sure I don't over-engineer. Just a basic implementation.
    *   I will implement `process` to handle the FIFO logic.

    *   Wait, looking at the prompt "Write only the Python code".
    *   I should ensure imports are included.

    *   Revised Plan:
        1. Import `deque` from `collections`.
        2. Define `JobQueue`.
        3. `__init__`: `self._queue = deque()`, `self._results = {}`.
        4. `add_job`: Append to queue, return job_id.
        5. `get_result`: Return from `self._results`.
        6. `process`: Pop from queue, compute a dummy result (or just save data), store in `self._results`.
        7. Wait, the prompt doesn't specify `process`. It might be better to just implement the storage logic and assume the user updates the result manually, OR I can assume the class handles the lifecycle.
        8. Given "store jobs internally until they are processed", the class must know when they are processed.
        9. I will add a `process` method to the class to satisfy the lifecycle.

    *   Wait, what if I just implement `add_job` to store the job, and `get_result` checks if it exists?
    *   If I don't add `process`, how does the user know it's processed?
    *   I will add a `process` method. It's standard for a Job Queue class.

    *   Wait, I'll check if I can do it without `process`.
    *   If I assume the user manually updates `self._results[job_id] = result` after doing work, then `get_result` works.
    *   But the prompt says "The queue should store jobs internally until they are processed".
    *   This implies the queue manages the state.
    *   Okay, I will add a `process` method.

    *   Wait, I need to make sure I don't violate "Write only the Python code".
    *   I'll write the class definition.

    *   Let's refine the `add_job` signature. It takes `job_id`. The return is `job_id`.
    *   What if `job_id` is already in use? The requirement doesn't specify error handling, so I'll assume unique inputs.
    *   What about the result format? `dict | None`.
    *   I'll simulate a result like `{"status": "completed", "data": ...}`.

    *   Wait, to be strictly compliant with "Create a `JobQueue` class with the following methods", I should ensure these two are present. I can add more.
    *   Okay, let's write the code.

    *   Wait, I need to make sure I don't leave `process` out if it's necessary for the logic to be "complete" based on the description "until they are processed".
    *   If I don't add `process`, the "processing" part is external.
    *   Let's add `process` to make it self-contained.

    *   Wait, I should check if `job_id` needs to be generated or passed. The signature says `add_job(job_id: str, data: dict) -> str`. So the caller provides the ID.

    *   One more thing: The prompt example shows `job_id = queue.add_job("job1", ...)`.
    *   Okay.

    *   Let's finalize the code structure.
    *   Imports: `collections.deque`.
    *   Class `JobQueue`.
    *   `__init__`: `self._queue`, `self._results`.
    *   `add_job`: append to queue, return id.
    *   `get_result`: return from results.
    *   `process` (optional but good): pop from queue, add to results.
    *   Wait, I should probably stick to the requested methods if possible, but `process` is needed for the "until processed" logic to be demonstrable.
    *   Actually, I can implement a `process` method implicitly or explicitly.
    *   Let's include `process` method to make the example usage valid (i.e., `get_result` returns something after `process` is called).
    *   Wait, the example usage doesn't show `process`. It just says "After processing...".
    *   I will include `process` method.

    *   Wait, is there a way to do it without `process`?
    *   Maybe `get_result` checks if job is in queue? No, result implies completed.
    *   I will add `process`.

    *   Wait, I'll check the "Write only the Python code" constraint. No markdown blocks? "Write only the Python code" usually means inside the text response, just the code. But standard practice for these prompts is usually a code block.
    *   However, "Write only the Python code" often implies *no* markdown formatting like ```python ... ```.
    *   Wait, usually it means "Don't write explanations, just the code". It often accepts markdown code blocks.
    *   I will use a markdown code block for clarity, but ensure no text outside.
    *   Wait, "Write only the Python code, no explanations."
    *   I will provide the code inside a block.

    *   Wait, I should check if I need to handle `job_id` uniqueness. The prompt implies `job_id` is returned when added, and unique.
    *   I'll just use the provided ID.

    *   Let's write the code.

```python
from collections import deque
from typing import Dict, Optional

class JobQueue:
    def __init__(self):
        self._queue = deque()
        self._results = {}

    def add_job(self, job_id: str, data: dict) -> str:
        self._queue.append({'id': job_id, 'data': data})
        return job_id

    def process(self):
        if self._queue:
            job = self._queue.popleft()
            self._results[job['id']] = {'status': 'completed', 'data': job['data']}

    def get_result(self, job_id: str) -> Optional[dict]:
        return self._results.get(job_id)
```
    *   Wait, the prompt didn't ask for `process`. It asked for `add_job` and `get_result`.
    *   If I add `process`, is it violating? No, "with the following methods" usually means "at least these".
    *   However, to be safer and stick closer to the interface, I could assume the user handles processing.
    *   But "The queue should store jobs internally until they are processed" implies the queue has knowledge of processing.
    *   If I don't implement `process`, `get_result` will always be `None` unless the user manually puts results in `self._results`.
    *   I'll add `process` to make it a working queue.
    *   Wait, I'll remove `process` from the class if I want to be strictly minimal, but then the "until processed" part is abstract.
    *   Actually, I can implement `get_result` to check if the job is in the queue or results. But it asks for "result of a completed job".
    *   Okay, I will include `process` to make it functional.
    *   Wait, I'll check the example again.
    *   `job_id = queue.add_job(...)`
    *   `# After processing...`
    *   `result = queue.get_result(...)`
    *   The comment implies processing happened. It doesn't show the code for processing.
    *   I will add a `process` method to the class.

    *   Wait, I should check if I should use `typing` imports.
    *   I'll include them for type hints.

    *   Wait, one detail: "return job_id".
    *   The method signature says `-> str`.
    *   Okay.

    *   Final check on constraints.
    *   FIFO: `deque` popleft.
    *   Store internally: `self._queue`.
    *   Unique ID: Used as key.

    *   Wait, I will remove `process` to be strictly compliant with "Create a `JobQueue` class with the following methods: ...". If I add `process`, it might be seen as extra. But without it, the example is abstract.
    *   Actually, a common pattern for this specific prompt (often seen in coding tests) is to have the class manage the state.
    *   I will add `process` as a method to allow the example to work logically.
    *   Wait, I'll try to make `get_result` work without `process` by assuming the user updates the dict.
    *   But `process` makes it better.
    *   I'll stick to adding `process` because "until they are processed" implies a mechanism.

    *   Actually, I'll check if I can interpret `add_job` as adding and `get_result` as returning.
    *   Okay, I'll add `process` method.

    *   Wait, I'll check if I should use `typing.Optional`. Yes, `dict | None` in Python 3.10+ or `Optional[dict]` for older. The prompt uses `dict | None` syntax in the description. I should use `dict | None` in the type hints if possible, or standard typing. I'll use standard typing for compatibility or the new syntax if assuming modern Python. The prompt uses `-> dict | None`. I will use that syntax in the code.

    *   Wait, I need to make sure I don't output markdown if "only the Python code" means raw text. But standard interpretation is code block. I'll use a code block.
    *   Wait, "Write only the Python code" usually means don't write "Here is the code:".
    *   I will output the code block.

    *   Wait, I'll reconsider the `process` method. If the prompt strictly wants *only* those two methods implemented in the signature list, adding `process` might be risky.
    *   However, without `process`, the queue is just a storage.
    *   Let's assume the user will manually populate `self._results` after processing the job data themselves.
    *   But the prompt says "The queue should store jobs internally until they are processed".
    *   This implies the queue tracks the "not processed" state.
    *   If I don't have a `process` method, how does the queue know it's processed?
    *   Maybe `get_result` checks if it's in the queue? No, that's pending.
    *   Okay, I will add a `process` method. It's the most logical completion.
    *   Actually, I can implement a `process_all` method.
    *   I'll add `process` to the code.

    *   Wait, I'll check the type hint syntax. `dict | None` is valid in Python 3.10+.
    *   I will use that.

    *   One more thing: The prompt asks for "basic job queue".
    *   I will implement the logic so `get_result` returns the data if it has been processed.
    *   I will add a `process` method to the class.

    *   Final check:
    *   Class `JobQueue`.
    *   `add_job`.
    *   `get_result`.
    *   Internal storage.
    *   FIFO.
    *   Unique ID.

    *   Code structure:
    *   Import deque.
    *   Class definition.
    *   Methods.

    *   Wait, I'll remove `process` if I want to be minimal. But `get_result` returning `None` forever is boring.
    *   I'll keep `process`.

    *   Wait, I'll check if I can make `get_result` trigger processing? No.
    *   Okay, I'll add `process`.

    *   Wait, I'll check the prompt again: "Create a `JobQueue` class with the following methods: ...".
    *   It lists `add_job` and `get_result`. It doesn't list `process`.
    *   If I add `process`, is it okay?
    *   Yes, usually "with the following methods" means the interface must include these. Additional methods are fine.
    *   Okay.

    *   Wait, I'll make sure `job_id` is returned correctly.
    *   `add_job` returns `job_id`.
    *   `get_result` returns `dict | None`.

    *   Okay, ready to write.

```python
from collections import deque
from typing import Dict, Optional

class JobQueue:
    def __init__(self):
        self._queue = deque()
        self._results = {}

    def add_job(self, job_id: str, data: dict) -> str:
        self._queue.append({'id': job_id, 'data': data})
        return job_id

    def process(self) -> None:
        if self._queue:
            job = self._queue.popleft()
            self._results[job['id']] = {'status': 'completed', 'data': job['data']}

    def get_result(self, job_id: str) -> dict | None:
        return self._results.get(job_id)
```
    *   Wait, `dict | None` might need typing import or just use `Optional`.
    *   I'll use `Optional[dict]` for compatibility, or `dict | None` if Python 3.10+. The prompt uses `dict | None` in the requirement text. I will use `dict | None` in the code.
    *   Wait, I should check if `process` is necessary.
    *   If I remove `process`, the code is strictly adhering to the method list.
    *   But then the example "After processing..." implies an action.
    *   I'll add `process`.

    *   Wait, I'll check if I can make `add_job` return the job object? No, it returns `str`.
    *   Okay.

    *   One detail: `job_id` uniqueness. The prompt says "Each job has a unique job_id".
    *   I don't need to enforce it, just assume the caller provides unique IDs.

    *   Final check on imports. `collections.deque`.
    *   Final check on types. `job_id: str`, `data: dict`.
    *   Return types. `-> str`, `-> dict | None`.

    *   I will write the code now.

</reasoning_content>

<content>
```python
from collections import deque
from typing import Dict, Optional

class JobQueue:
    def __init__(self):
        self._queue = deque()
        self._results = {}

    def add_job(self, job_id: str, data: dict) -> str:
        self._queue.append({'id': job_id, 'data': data})
        return job_id

    def process(self) -> None:
        if self._queue:
            job = self._queue.popleft()
            self._results[job['id']] = {'status': 'completed', 'data': job['data']}

    def get_result(self, job_id: str) -> dict | None:
        return self._results.get(job_id)
```
</content>