We are currently solving the following issue within our repository. Here is the issue text:
--- BEGIN ISSUE ---
Missing type annotation in `strawberry.fastapi.BaseContext` causes mypy to trip
## Describe the Bug

I built a custom context based on [the guide in the docs](https://strawberry.rocks/docs/guides/authentication):

```python
from strawberry.fastapi import BaseContext

class CustomContext(BaseContext):
    @property
    def user(self) -> User:
        ...

async def get_context() -> CustomContext:
    return CustomContext()
```

With that I receive the following mypy error:
```shell
 error: Call to untyped function "CustomContext" in typed context  [no-untyped-call]
```

For now, I added the following workaround to my code:
```python
class CustomContext(BaseContext):
    if typing.TYPE_CHECKING:
        def __init__(self) -> None:
            pass
    
    ...
```

## System Information

 - Operating system: macOS Monterey
 - Strawberry version (if applicable): `0.158.1`
 - FastAPI version (if applicable): `0.92.0`
 - mypy version (if applicable): `0.991` (also tested with `1.0.1`)

## Additional Context

I'm happy to provide a PR to address the issue myself.


--- END ISSUE ---

Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
--- BEGIN FILES ---
Path: `strawberry/fastapi/context.py`
Content:
```
1 from typing import Any, Dict, Optional, Union
2 
3 from starlette.background import BackgroundTasks
4 from starlette.requests import Request
5 from starlette.responses import Response
6 from starlette.websockets import WebSocket
7 
8 CustomContext = Union["BaseContext", Dict[str, Any]]
9 MergedContext = Union[
10     "BaseContext", Dict[str, Union[Any, BackgroundTasks, Request, Response, WebSocket]]
11 ]
12 
13 
14 class BaseContext:
15     connection_params: Optional[Any] = None
16 
17     def __init__(self):
18         self.request: Optional[Union[Request, WebSocket]] = None
19         self.background_tasks: Optional[BackgroundTasks] = None
20         self.response: Optional[Response] = None
21
```
--- END FILES ---

Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.

Here is an example:

```diff
diff --git a/examples/server_async.py b/examples/server_async.py
--- a/examples/server_async.py
+++ b/examples/server_async.py
@@ -313,4 +313,4 @@
 
 
 if __name__ == "__main__":
-    asyncio.run(run_async_server("."), debug=True)
+    asyncio.run(run_async_server(), debug=True)
diff --git a/examples/server_sync.py b/examples/server_sync.py
--- a/examples/server_sync.py
+++ b/examples/server_sync.py
@@ -313,5 +313,5 @@
 
 
 if __name__ == "__main__":
-    server = run_sync_server(".")
+    server = run_sync_server()
     server.shutdown()

```

diff --git a/strawberry/fastapi/context.py b/strawberry/fastapi/context.py
--- a/strawberry/fastapi/context.py
+++ b/strawberry/fastapi/context.py
@@ -14,7 +14,7 @@
 class BaseContext:
     connection_params: Optional[Any] = None
 
-    def __init__(self):
+    def __init__(self) -> None:
         self.request: Optional[Union[Request, WebSocket]] = None
         self.background_tasks: Optional[BackgroundTasks] = None
         self.response: Optional[Response] = None

{"golden_diff": "diff --git a/strawberry/fastapi/context.py b/strawberry/fastapi/context.py\n--- a/strawberry/fastapi/context.py\n+++ b/strawberry/fastapi/context.py\n@@ -14,7 +14,7 @@\n class BaseContext:\n     connection_params: Optional[Any] = None\n \n-    def __init__(self):\n+    def __init__(self) -> None:\n         self.request: Optional[Union[Request, WebSocket]] = None\n         self.background_tasks: Optional[BackgroundTasks] = None\n         self.response: Optional[Response] = None\n", "issue": "Missing type annotation in `strawberry.fastapi.BaseContext` causes mypy to trip\n## Describe the Bug\r\n\r\nI built a custom context based on [the guide in the docs](https://strawberry.rocks/docs/guides/authentication):\r\n\r\n```python\r\nfrom strawberry.fastapi import BaseContext\r\n\r\nclass CustomContext(BaseContext):\r\n    @property\r\n    def user(self) -> User:\r\n        ...\r\n\r\nasync def get_context() -> CustomContext:\r\n    return CustomContext()\r\n```\r\n\r\nWith that I receive the following mypy error:\r\n```shell\r\n error: Call to untyped function \"CustomContext\" in typed context  [no-untyped-call]\r\n```\r\n\r\nFor now, I added the following workaround to my code:\r\n```python\r\nclass CustomContext(BaseContext):\r\n    if typing.TYPE_CHECKING:\r\n        def __init__(self) -> None:\r\n            pass\r\n    \r\n    ...\r\n```\r\n\r\n## System Information\r\n\r\n - Operating system: macOS Monterey\r\n - Strawberry version (if applicable): `0.158.1`\r\n - FastAPI version (if applicable): `0.92.0`\r\n - mypy version (if applicable): `0.991` (also tested with `1.0.1`)\r\n\r\n## Additional Context\r\n\r\nI'm happy to provide a PR to address the issue myself.\r\n\n", "before_files": [{"content": "from typing import Any, Dict, Optional, Union\n\nfrom starlette.background import BackgroundTasks\nfrom starlette.requests import Request\nfrom starlette.responses import Response\nfrom starlette.websockets import WebSocket\n\nCustomContext = Union[\"BaseContext\", Dict[str, Any]]\nMergedContext = Union[\n    \"BaseContext\", Dict[str, Union[Any, BackgroundTasks, Request, Response, WebSocket]]\n]\n\n\nclass BaseContext:\n    connection_params: Optional[Any] = None\n\n    def __init__(self):\n        self.request: Optional[Union[Request, WebSocket]] = None\n        self.background_tasks: Optional[BackgroundTasks] = None\n        self.response: Optional[Response] = None\n", "path": "strawberry/fastapi/context.py"}], "after_files": [{"content": "from typing import Any, Dict, Optional, Union\n\nfrom starlette.background import BackgroundTasks\nfrom starlette.requests import Request\nfrom starlette.responses import Response\nfrom starlette.websockets import WebSocket\n\nCustomContext = Union[\"BaseContext\", Dict[str, Any]]\nMergedContext = Union[\n    \"BaseContext\", Dict[str, Union[Any, BackgroundTasks, Request, Response, WebSocket]]\n]\n\n\nclass BaseContext:\n    connection_params: Optional[Any] = None\n\n    def __init__(self) -> None:\n        self.request: Optional[Union[Request, WebSocket]] = None\n        self.background_tasks: Optional[BackgroundTasks] = None\n        self.response: Optional[Response] = None\n", "path": "strawberry/fastapi/context.py"}]}