You write standard Python with types:

```Python
from datetime import date

from pydantic import BaseModel

# Declare a variable as a str
# and get editor support inside the function
def main(user_id: str):
    return user_id


# A Pydantic model
class User(BaseModel):
    id: int
    name: str
    joined: date
```

That can then be used like:

```Python

# above is tagged with "py3-none-any". We cannot change the tags by simply
# renaming the wheels as uploading to PyPI would fail with "File already exists"
# error. In order to upload to PyPI, we unpack the wheel and change the tag
# inside a metadata file to the one we want (e.g cp38-cp38-win_amd) and then
# re-pack it to generate it as a platform specific wheel with this new wheel
#tag.
python3 -m wheel unpack "${pure_python_whl}"

```Python
app.dependency_overrides = {}
```

/// tip

If you want to override a dependency only during some tests, you can set the override at the beginning of the test (inside the test function) and reset it at the end (at the end of the test function).

   */
  public static Splitter on(char separator) {
    return on(CharMatcher.is(separator));
  }

  /**
   * Returns a splitter that considers any single character matched by the given {@code CharMatcher}
   * to be a separator. For example, {@code
   * Splitter.on(CharMatcher.anyOf(";,")).split("foo,;bar,quux")} returns an iterable containing

You can use `async def` or normal `def`.

And you can declare dependencies with `async def` inside of normal `def` *path operation functions*, or `def` dependencies inside of `async def` *path operation functions*, etc.

It doesn't matter. **FastAPI** will know what to do.

/// note

```Python hl_lines="7"
{!../../docs_src/path_params/tutorial002.py!}
```

In this case, `item_id` is declared to be an `int`.

/// check

This will give you editor support inside of your function, with error checks, completion, etc.

///

## Data <abbr title="also known as: serialization, parsing, marshalling">conversion</abbr>

First, write all your **FastAPI** application as normally:

{* ../../docs_src/extending_openapi/tutorial001.py hl[1,4,7:9] *}

### Generate the OpenAPI schema

Then, use the same utility function to generate the OpenAPI schema, inside a `custom_openapi()` function:

{* ../../docs_src/extending_openapi/tutorial001.py hl[2,15:21] *}

### Modify the OpenAPI schema

Then, behind the scenes, it would put that JSON-compatible data (e.g. a `dict`) inside of a `JSONResponse` that would be used to send the response to the client.

But you can return a `JSONResponse` directly from your *path operations*.

It might be useful, for example, to return custom headers or cookies.

# Dependencies in path operation decorators

In some cases you don't really need the return value of a dependency inside your *path operation function*.

Or the dependency doesn't return a value.

But you still need it to be executed/solved.

For those cases, instead of declaring a *path operation function* parameter with `Depends`, you can add a `list` of `dependencies` to the *path operation decorator*.

     * are not listed in a user's group membership (e.g. as represented by the
     * tokenGroups constructed attribute retrieved via LDAP).
     * <p/>
     * Domain groups nested inside a local group are currently not expanded. In
     * this case the key (SID) type will be SID_TYPE_DOM_GRP rather than
     * SID_TYPE_USER.
     * 
     * @param tc
     *            The context to use