<reasoning_content>
*   Goal: Implement a basic job queue in Python.
    *   Requirements:
        *   Class `JobQueue` with `add_job(job_id, data)` and `get_result(job_id)`.
        *   FIFO order.
        *   Store jobs internally until processed.
        *   Unique `job_id` returned.
    *   Constraints: Write only Python code, no explanations.

    *   `collections.deque` is ideal for a FIFO queue.
    *   A dictionary to store the results mapping `job_id` to the result.
    *   Since the prompt doesn't specify *who* processes the job (asynchronous worker vs simple list storage), but the prompt says "The queue should store jobs internally until they are processed", I should probably simulate the storage of results once "processed".
    *   Wait, the prompt implies a sequence: `add_job`, then "After processing...", then `get_result`.
    *   How does the job get "processed"? The prompt doesn't have a `process_jobs()` method, but `get_result` implies that once a job is done, it's available.
    *   Actually, looking at the example:
        ```python
        job_id = queue.add_job("job1", {"task": "process_data"})
        # After processing...
        result = queue.get_result("job1")
        ```
        This suggests that there might be an internal mechanism or a manual way to set the result. However, usually, in these coding prompts, "processing" might be mocked or I might need a `complete_job` helper or just a way for the system to mark it done.
    *   Rethink: If the user says "The queue should store jobs internally until they are processed", and there is no `process` method requested, maybe I should implement a simple logic where `get_result` returns the result if it exists.
    *   Wait, if I don't have a `process` method, how does the data move from "queued" to "result"?
    *   Let's look at the signature again: `add_job(job_id: str, data: dict) -> str`. It returns the `job_id`. This implies the user provides the ID.
    *   Let's check if I should simulate a worker or just provide the structure.
    *   Actually, a standard "Job Queue" implementation usually has a way to complete a job. Since the prompt doesn't define a `complete_job` method, I should probably include a private/internal way or just assume `get_result` checks if it's done.
    *   Actually, looking at the requirements: "The queue should store jobs internally until they are processed".
    *   Let's assume a scenario where the job result is stored in a dictionary once "processed". Since no process method is provided, I'll add a method `complete_job` (or similar) even if not requested, OR I'll make `get_result` handle the logic.
    *   Wait, the prompt says: "Write only the Python code".
    *   Let's refine the `JobQueue` class.
    *   Internal storage: `self.queue` (deque for order), `self.results` (dict).
    *   `add_job`: puts into deque and dict (initially result is None/Pending).
    *   `get_result`: returns from dict.

    Wait, if I don't have a way to *complete* the job in the provided API, how does the result get populated?
    Perhaps the "processing" is implied to be handled by a consumer.
    Let's stick strictly to the requested methods.

    Actually, I'll add a `complete_job` method internally or just use a dict to store the state. If the user doesn't provide a way to complete it, `get_result` will always return `None` unless I provide a mechanism.
    Let's look at the example again. `# After processing...` implies something happens between `add_job` and `get_result`.
    I will provide a `complete_job` method as well to make it functional, or just stick to the requested methods and assume the user might call a method I define or the data is modified.
    Actually, I'll just provide the two requested methods. To make it "functional" for a test, I'll add a `complete_job` method.

    *Actually*, looking at "Requirements: Create a JobQueue class with the following methods...", I should probably only include those.
    Wait, if I only provide those two, how does the job actually finish?
    Maybe the `data` passed in `add_job` is used to determine the result?
    No, "After processing..." is a comment.

    Let's implement it such that `add_job` stores the job in a queue, and `get_result` checks a storage. I'll add a `complete_job` method to allow the "processing" to happen.

    Actually, let's look at Requirement 3: "The queue should store jobs internally until they are processed".
    Requirement 1: `add_job`, `get_result`.

    Maybe I'll implement a simple mock processor or just the storage.
    Let's go with:
    - `self._queue`: deque for FIFO.
    - `self._results`: dict mapping `job_id` to result.
    - `self._jobs`: dict mapping `job_id` to the original data.
    - `add_job`: check if id exists, add to deque and dicts.
    - `get_result`: return from dict.
    - To satisfy "until they are processed", I'll add a `complete_job` method to actually allow the state change.

    Revised plan:
    Include `add_job` and `get_result`.
    Since `complete_job` wasn't asked for, but "processing" is mentioned, I'll add a helper `complete_job` or just implement the storage.

    Wait, looking at the prompt again, it's a coding task. Usually, they want the specific methods.
    I will provide the two requested methods and a `complete_job` method so the example works.

    Wait, I'll just stick to the requested ones and make `get_result` return the value from a dictionary. I'll add `complete_job` anyway because it's logically necessary for the example to work.

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

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

        def add_job(self, job_id: str, data: dict) -> str:
            if job_id in self._results or job_id in self._jobs:
                raise ValueError("Job ID already exists")
            self._jobs[job_id] = data
            self._queue.append(job_id)
            self._results[job_id] = None
            return job_id

        def complete_job(self, job_id: str, result: dict):
            # Not explicitly requested but necessary for the flow
            self._results[job_id] = result

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

    Wait, the prompt says "Write only the Python code, no explanations."
    I should make sure the code is clean.

    Refining the requirements:
    - `add_job` returns `job_id`.
    - FIFO order.
    - Store until processed.

    If I don't have a `process` method, I'll just implement the requested ones.

    One detail: "The queue should store jobs internally until they are processed".
    If I store them in a deque, I'm following FIFO.

    Final Code Structure:
    ```python
    from collections import deque
    from typing import Dict, Any, Optional

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

        def add_job(self, job_id: str, data: dict) -> str:
            if job_id in self.results or job_id in self.jobs:
                raise ValueError(f"Job ID {job_id} already exists.")
            self.jobs[job_id] = data
            self.queue.append(job_id)
            self.results[job_id] = None
            return job_id

        def complete_job(self, job_id: str, result: dict):
            if job_id in self.jobs:
                self.results[job_id] = result
                # Once completed, we could remove from jobs if desired
                # but prompt says "store ... until processed".
                # So I'll leave it in jobs until removed or until completion.
                pass

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

    Actually, to be strictly compliant with the instructions, I'll keep it simple.

    Wait, I'll provide a way to process jobs or the user will find it impossible to use the example.
    The example says `# After processing...`. This implies the user is expected to "process" it.
    How does the `JobQueue` know it's processed?
    Maybe `get_result` returns `None` until a `complete_job` (or similar) is called.

    I will add `complete_job` to make the example usable.
</reasoning_content>

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

class JobQueue:
    def __init__(self):
        # Stores the order of jobs to be processed (FIFO)
        self._queue: deque[str] = deque()
        # Stores the raw job data
        self._jobs: Dict[str, dict] = {}
        # Stores the final results of processed jobs
        self._results: Dict[str, dict] = {}

    def add_job(self, job_id: str, data: dict) -> str:
        """
        Adds a job to the queue.
        """
        if job_id in self._jobs or job_id in self._results:
            raise ValueError(f"Job ID {job_id} already exists.")
        
        self._jobs[job_id] = data
        self._queue.append(job_id)
        self._results[job_id] = None
        return job_id

    def complete_job(self, job_id: str, result: dict):
        """
        Helper method to simulate the processing of a job 
         and store its result.
        """
        if job_id in self._jobs:
            self._results[job_id] = result
            # Remove from internal job storage once processed
            del self._jobs[job_id]
            # Remove from queue if it's still there
            if job_id in self._queue:
                self._queue.remove(job_id)

    def get_result(self, job_id: str) -> dict | None:
        """
        Retrieves the result of a completed job.
        """
        return self._results.get(job_id)
```
</content>