{* ../../docs_src/path_params/tutorial002.py hl[7] *}

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> { #data-conversion }

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.

5. Copy the `./app` directory inside the `/code` directory.

    As this has all the code which is what **changes most frequently** the Docker **cache** won't be used for this or any **following steps** easily.

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

### Generate the OpenAPI schema { #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 { #modify-the-openapi-schema }

{* ../../docs_src/security/tutorial002_an_py310.py hl[31] *}

Notice that we declare the type of `current_user` as the Pydantic model `User`.

This will help us inside of the function with all the completion and type checks.

/// tip

You might remember that request bodies are also declared with Pydantic models.

Here **FastAPI** won't get confused because you are using `Depends`.

#### Union { #union }

You can declare that a variable can be any of **several types**, for example, an `int` or a `str`.

In Python 3.6 and above (including Python 3.10) you can use the `Union` type from `typing` and put inside the square brackets the possible types to accept.

     * are not listed in a user's group membership (e.g. as represented by the
     * tokenGroups constructed attribute retrieved via LDAP).
     *
     * 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

    BufferedReader reader = openBufferedStream();
    return reader.lines().onClose(() -> closeUnchecked(reader));
  }

  @IgnoreJRERequirement // helper for lines()
  /*
   * If we make these calls inline inside the lambda inside lines(), we get an Animal Sniffer error,
   * despite the @IgnoreJRERequirement annotation there. For details, see ImmutableSortedMultiset.
   */
  private static void closeUnchecked(Closeable closeable) {

    BufferedReader reader = openBufferedStream();
    return reader.lines().onClose(() -> closeUnchecked(reader));
  }

  @IgnoreJRERequirement // helper for lines()
  /*
   * If we make these calls inline inside the lambda inside lines(), we get an Animal Sniffer error,
   * despite the @IgnoreJRERequirement annotation there. For details, see ImmutableSortedMultiset.
   */
  private static void closeUnchecked(Closeable closeable) {

 * has zero slope).
 *
 * @author Pete Gillin
 * @since 20.0
 */
@J2ktIncompatible
@GwtIncompatible
public abstract class LinearTransformation {
  /**
   * Constructor for use by subclasses inside Guava.
   *
   * @deprecated Create instances by using the static factory methods of the class.
   */
  @Deprecated
  public LinearTransformation() {}

  /**