Retrieve a file

You're Claude Code, working in my repository.

Task
Add a get_file helper to my app that calls GET https://api.meta.ai/v1/files/{file_id} and returns the FileObject, returning None (or null) for a 404 instead of raising.

Read this first
Meta's docs page "Retrieve a file" as Markdown: https://dev.meta.ai/docs/api-reference/files/retrieve-file.md
It's the source of truth for request and response shapes. The same page for people: https://dev.meta.ai/docs/api-reference/files/retrieve-file

Setup
- Base URL: https://api.meta.ai/v1
- Auth: send Authorization: Bearer $MODEL_API_KEY, reading MODEL_API_KEY from the environment. Never hard-code, print or commit the key.
- Model: muse-spark-1.3-contributor (Contributor mode: Meta may use what you send to train future models; drop -contributor for Standard mode)
- Python: the OpenAI SDK (pip install openai) with base_url="https://api.meta.ai/v1" and api_key=os.environ["MODEL_API_KEY"] works, or plain requests.

Facts to get right
- file_id is a required path parameter, such as file-842549258569145.
- The reply is a FileObject: {"id", "bytes", "created_at", "expires_at", "filename", "object": "file", "purpose", "status"}. expires_at may be null or missing when the file never expires; status and status_details are deprecated.
- A deleted or unknown id answers 404. For the bytes, call GET /v1/files/{file_id}/content.

Starter code (Python)
import os

import requests


def get_file(file_id):
    response = requests.get(
        f"https://api.meta.ai/v1/files/{file_id}",
        headers={"Authorization": f"Bearer {os.environ['MODEL_API_KEY']}"},
    )
    if response.status_code == 404:
        return None
    response.raise_for_status()
    return response.json()


print(get_file("file_abc123"))

Done when
- get_file on a fresh upload returns its filename and bytes.
- get_file on a deleted id returns None.
- The key comes from MODEL_API_KEY and never appears in code, logs or commits.
- API errors (4xx, 429) surface their message instead of failing silently.