{* ../../docs_src/dependencies/tutorial008_an_py39.py hl[18:19,26:27] *}

The same way, you could have some dependencies with `yield` and some other dependencies with `return`, and have some of those depend on some of the others.

And you could have a single dependency that requires several other dependencies with `yield`, etc.

    * A "token" is just a string with some content that we can use later to verify this user.
    * Normally, a token is set to expire after some time.
        * So, the user will have to log in again at some point later.
        * And if the token is stolen, the risk is less. It is not like a permanent key that will work forever (in most of the cases).

</div>

## Forbid Extra Headers { #forbid-extra-headers }

In some special use cases (probably not very common), you might want to **restrict** the headers that you want to receive.

You can use Pydantic's model configuration to `forbid` any `extra` fields:

{* ../../docs_src/header_param_models/tutorial002_an_py310.py hl[10] *}

If a client tries to send some **extra headers**, they will receive an **error** response.

The next sections assume you already read the main [Tutorial - User Guide: Security](../../tutorial/security/index.md){.internal-link target=_blank}.

* Each application that you have running on your computer has some process behind it, each running program, each window, etc. And there are normally many processes running **at the same time** while a computer is on.
* There can be **multiple processes** of the **same program** running at the same time.

def test_route_converters_path():
    # Test path conversion
    response = client.get("/path/some/example")
    assert response.status_code == 200, response.text
    assert response.json() == {"path": "some/example"}


def test_route_converters_query():
    # Test query conversion
    response = client.get("/query", params={"param": "Qué tal!"})

## Overriding dependencies during testing { #overriding-dependencies-during-testing }

There are some scenarios where you might want to override a dependency during testing.

You don't want the original dependency to run (nor any of the sub-dependencies it might have).

https://github.com/google/guava/graphs/contributors. However, Git history
over-counts some people's contributions because they were responsible for
mirroring out changes from our internal repo.

This files serves mainly to credit people who have not received proper credit
in the Git history.

Doug Lea, author of some concurrency libraries

Joshua O'Madadhain (@jrtom), author of some common.graph commits beyond those

   *
   * @return the next two bytes of the input stream, interpreted as an unsigned 16-bit integer in
   *     little-endian byte order
   * @throws IOException if an I/O error occurs
   */
  @CanIgnoreReturnValue // to skip some bytes
  @Override
  public int readUnsignedShort() throws IOException {
    byte b1 = readAndCheckByte();
    byte b2 = readAndCheckByte();

    return Ints.fromBytes((byte) 0, (byte) 0, b2, b1);
  }

                    public String[] baz() { return new String[] {"some"}; }
                }
            """,
            v2 = """
                public class Source {
                    @$nullUnmarkedAnnotationName public String foo() { return "bar"; }
                    public @$nullUnmarkedAnnotationName String[] baz() { return new String[] {"some", null}; }
                }
            """
        ) {