<reasoning_content>
*   Goal: Implement a basic job queue in Python.
    *   Class Name: `JobQueue`.
    *   Method 1: `add_job(job_id: str, data: dict) -> str`. Returns `job_id`.
    *   Method 2: `get_result(job_id: str) -> dict | None`. Returns the result or None.
    *   Ordering: FIFO (First-In-First-Out).
    *   Storage: Internal storage for jobs until processed.
    *   Requirement: Unique `job_id` (although the prompt says the user provides `job_id` in the method signature, the signature `add_job(job_id: str, ...)` suggests the user provides it, but then says "Each job has a unique job_id that is returned". I should probably check if the provided ID exists or just store it). Wait, the signature is `add_job(job_id: str, ...)`. If the user passes the ID, I'll use that.
    *   Constraint: Write only Python code, no explanations.

    *   Need a data structure for the FIFO queue (e.g., `collections.deque`).
    *   Need a data structure to store job statuses/results (e.g., a dictionary mapping `job_id` to its result).
    *   Need a mechanism to simulate "processing" or at least a way to "finish" a job so `get_result` works. Since the prompt doesn't specify a worker thread/process, I'll provide a way to complete a job (perhaps a `complete_job` method) or just assume the queue stores data and `get_result` looks it up.
    *   *Re-reading requirements*: "The queue should store jobs internally until they are processed." and `get_result` should return the result of a *completed* job.
    *   If I just have `add_job` and `get_result`, how does a job get "completed"? Usually, there's a `process` or `complete` method. If not provided, maybe I should implement a dummy processing logic or a `complete_job` method to make the example work?
    *   Wait, the example shows:
        ```python
        job_id = queue.add_job("job1", {"task": "process_data"})
        # After processing...
        result = queue.get_result("job1")
        ```
    *   To make this work, I need a way to set the result. I'll add a `complete_job` method or similar, even though it's not explicitly in the requirements, because `get_result` would always be `None` otherwise. Or, maybe the user expects the `JobQueue` to have an internal worker? But the requirements are "Basic".
    *   Actually, let's look at the requirements again.
        1. `add_job(job_id, data)`
        2. `get_result(job_id)`
        3. FIFO.
    *   To satisfy FIFO, I need a queue. To satisfy `get_result`, I need a storage for results.
    *   Since there's no "process" method requested, I will add a `complete_job` method to allow the result to be set, otherwise the example code provided in the prompt won't actually return anything other than `None`.

    *Refined Plan*:
    - Use `collections.deque` for the queue of jobs.
    - Use a dictionary `results` to store results.
    - `add_job`: push to deque, store initial data.
    - `get_result`: check `results` dict.
    - I'll add a `complete_job(job_id, result)` method to make the example usable.

    *Wait, let's look at the prompt again.* "Write only the Python code". It doesn't say "Only implement these two methods". It says "Create a JobQueue class with the following methods". It doesn't forbid others. However, I should stick as close to requirements as possible.

    Wait, if I don't have a way to process, `get_result` will always be `None`. I will include a `complete_job` method.

    Wait, looking at the example: `result = queue.get_result("job1")`. If `job1` is just added, and no processing happens, it's `None`.

    Let's implement exactly what's asked.

    ```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 get_result(self, job_id: str) -> dict | None:
            return self.results.get(job_id)

        def complete_job(self, job_id: str, result: dict) -> None:
            self.results[job_id] = result
    ```

    Actually, looking at the requirements again: "Jobs should be processed in FIFO ( First-In-First-Out) order". This implies a `process` mechanism.

    Let's try a version where `process_next_job` exists.

    Revised requirements check:
    1. `add_job` returns `job_id`.
    2. `get_result` returns result.
    3. FIFO.
    4. Store internally.
    5. Unique `job_id`.

    Wait, if the user provides `job_id` in the argument, is it unique? I should check if it's already in use.

    Actually, a standard "Job Queue" implementation usually involves a worker. But for a "basic" one without threading requirements, a simple list/deque and a dict is standard.

    I will provide the requested methods and a `complete_job` method so the example is functional.

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

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

        def add_job(self, job_id: str, data: dict) -> str:
            if job_id in self._job_ids:
                raise ValueError("Job ID already exists")
            
            self._queue.append({"id": job_id, "data": data})
            self._job_ids.add(job_id)
            return job_id

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

        def complete_job(self, job_id: str, result: dict) -> None:
            self._results[job_id] = result
    ```

    Actually, if I strictly follow "Write only the Python code", and the prompt says "Create a JobQueue class with the following methods", usually implies *only* those or at least those. I'll stick to those and maybe a `complete_job` to make sense of "processed".

    Wait, "Jobs should be processed in FIFO order". If I don't have a `process` method, how are they processed?
    Maybe the prompt implies that the queue *is* the storage and `get_result` is just a lookup.

    Let's refine the `add_job` to ensure `job_id` is unique as requested ("Each job has a unique job_id").

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

    class JobQueue:
        def __init__(self):
            self.queue = deque()
            self.results = {}
            self.active_ids = set()

        def add_job(self, job_id: str, data: dict) -> str:
            if job_id in self.active_ids:
                raise ValueError("Job ID must be unique")
            
            self.queue.append({"id": job_id, "data": data})
            self.active_ids.add(job_id)
            return job_id

        def get_result(self, job_id: str) -> dict | None:
            return self.results.get(job_id)

        def complete_job(self, job_id: str, result: dict) -> None:
            self.results[job_id] = result
    ```

    Actually, looking at the prompt's example:
    `# After processing...`
    This implies there is an external process or a missing method. I'll include `complete_job`.

    One more thing: "The queue should store jobs internally until they are processed".
    I will keep them in the `deque` until they are "processed".

    Revised code structure:
    ```python
    from collections import deque
    from typing import Dict, Optional

    class JobQueue:
        def __init__(self):
            self.queue = deque()
            self.results = {}
            self.used_ids = set()

        def add_job(self, job_id: str, data: dict) -> str:
            if job_id in self.used_ids:
                raise ValueError("Job ID must be unique")
            self.queue.append({"id": job_id, "data": data})
            self.used_ids.add(job_id)
            return job_id

        def get_result(self, job_id: str) -> dict | None:
            return self.results.get(job_id)

        def complete_job(self, job_id: str, result: dict) -> None:
            # In a real system, this would also remove from queue
            self.results[job_id] = result
            # Removing from queue isn't strictly required by the signature
            # but makes sense for "until they are processed"
            for i, item in enumerate(self.queue):
                if item["id"] == job_id:
                    del self.queue[i]
                    break
    ```
    Actually, "processed in FIFO order" means the removal from the queue should be the first item.

    Let's simplify. The user wants a "basic" queue.

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

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

        def add_job(self, job_id: str, data: dict) -> str:
            if job_id in self._seen_ids:
                raise ValueError("Job ID must be unique")
            self._queue.append({"id": job_id, "data": data})
            self._seen_ids.add(job_id)
            return job_id

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

        def complete_job(self, job_id: str, result: dict) -> None:
            self._results[job_id] = result
            # To maintain FIFO and "until processed" logic:
            # We find the job in the queue and remove it.
            # But a basic queue usually just pops from the left.
            # Since we need to complete specific IDs (from get_result),
            # we'll just store results.
    ```

    Actually, I'll just provide the required methods and a helper to complete them.

    One last check: "Jobs should be processed in FIFO order".
    If I don't have a `process_next` method, the only way to respect FIFO is if a worker pulls from the front of the `deque`.

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

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

        def add_job(self, job_id: str, data: dict) -> str:
            if job_id in self._used_ids:
                raise ValueError("Job ID must be unique")
            self._queue.append({"id": job_id, "data": data})
            self._used_ids.add(job_id)
            return job_id

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

        def complete_job(self, job_id: str, result: dict) -> None:
            self._results[job_id] = result
            # Removing from the queue to signify it is "processed"
            # In FIFO, the first item is usually processed first.
            # However, the user might complete jobs out of order in a multi-threaded env.
            # But for a "basic" queue, let's just manage results.
    ```

    Actually, I'll keep it simple. The requirements are minimal.

    Final check on requirements:
    1. `add_job` -> returns `job_id`. (Done)
    2. `get_result` -> returns `dict | None`. (Done)
    3. FIFO. (Using `deque`)
    4. Store until processed. (Storing in `deque`)
    5. Unique `job_id`. (Checking `set`)

    I will add `complete_job` because without it, `get_result` is useless for the example.
</reasoning_content>

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

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

    def add_job(self, job_id: str, data: dict) -> str:
        """
        Adds a job to the queue.
        Returns the job_id.
        """
        if job_id in self._seen_ids:
            raise ValueError("Job ID must be unique")
        
        self._queue.append({"id": job_id, "data": data})
        self._seen_ids.add(job_id)
        return job_id

    def get_result(self, job_id: str) -> dict | None:
        """
        Returns the result of a completed job, or None if not completed.
        """
        return self._results.get(job_id)

    def complete_job(self, job_id: str, result: dict) -> None:
        """
        Marks a job as completed and stores its result.
         This is used to transition a job from 'pending' to 'completed'.
        """
        self._results[job_id] = result
        
        # Remove from the internal queue to signify it is processed
        for i, item in enumerate(self._queue):
            if item["id"] == job_id:
                del self._queue[i]
                break
```
</content>