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
my_user: User = User(id=3, name="John Doe", joined="2018-07-19")

second_user_data = {
    "id": 4,
    "name": "Mary",
    "joined": "2018-11-30",
}

my_second_user: User = User(**second_user_data)
```

/// info

## Dependency Injection

Using `BackgroundTasks` also works with the dependency injection system, you can declare a parameter of type `BackgroundTasks` at multiple levels: in a *path operation function*, in a dependency (dependable), in a sub-dependency, etc.

    return proxyClass.isInstance(arg)
        // Equal proxy instances should mostly be instance of proxyClass
        // Under some edge cases (such as the proxy of JDK types serialized and then deserialized)
        // the proxy type may not be the same.
        // We first check isProxyClass() so that the common case of comparing with non-proxy objects
        // is efficient.

So:

```Python
q: Union[str, None] = Query(default=None)
```

...makes the parameter optional, with a default value of `None`, the same as:

```Python
q: Union[str, None] = None
```

And in Python 3.10 and above:

						return nil, setupType,
							config.ErrInvalidErasureEndpoints(nil).Msg(fmt.Sprintf("same path '%s' can not be served by different port on same address", endpoint.Path))
					}
					pathIPMap[endpoint.Path] = IPSet.Union(hostIPSet)
				} else {
					pathIPMap[endpoint.Path] = hostIPSet
				}
			}
		}

		// Check whether same path is used for more than 1 local endpoints.
		{

  abstract int distinctElements();

  // Object methods

  /**
   * {@inheritDoc}
   *
   * <p>This implementation returns {@code true} if {@code object} is a multiset of the same size
   * and if, for each element, the two multisets have the same count.
   */
  @Override
  public final boolean equals(@CheckForNull Object object) {
    return Multisets.equalsImpl(this, object);
  }

  /**
   * {@inheritDoc}

   * exactly one entry for each distinct element in the multiset (thus it always has the same size
   * as the {@link #elementSet}). The order of the elements in the element set is unspecified.
   *
   * <p>The entry set is backed by the same data as the multiset, so any change to either is
   * immediately reflected in the other. However, multiset changes may or may not be reflected in

	STREX	R1, (R0), R1       // ERROR "cannot use same register as both source and destination"
	STREX	R1, (R0), R0       // ERROR "cannot use same register as both source and destination"
	STREXD	R0, (R2), R0       // ERROR "cannot use same register as both source and destination"
	STREXD	R0, (R2), R1       // ERROR "cannot use same register as both source and destination"
	STREXD	R0, (R2), R2       // ERROR "cannot use same register as both source and destination"

        endpoint: Callable[..., Any],
        *,
        name: Optional[str] = None,
        dependencies: Optional[Sequence[params.Depends]] = None,
        dependency_overrides_provider: Optional[Any] = None,
    ) -> None:
        self.path = path
        self.endpoint = endpoint
        self.name = get_name(endpoint) if name is None else name
        self.dependencies = list(dependencies or [])

   * </ol>
   *
   * @param multimap the presumed-immutable multimap
   * @param sampleKey a key of the same type as that contained by {@code multimap}. {@code multimap}
   *     may or may not have {@code sampleKey} as a key.
   * @param sampleValue a key of the same type as that contained by {@code multimap}. {@code
   *     multimap} may or may not have {@code sampleValue} as a key.
   */