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

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

## Return a `Response` { #return-a-response }

In fact, you can return any `Response` or any sub-class of it.

/// tip

    assertEquals("null=null", entry(NK, NV).toString());
  }

  public void testEquals() {
    Entry<String, Integer> foo1 = entry("foo", 1);
    // Explicitly call `equals`; `assertEquals` might return fast
    assertTrue(foo1.equals(foo1));
    assertEquals(control("foo", 1), foo1);
    assertEquals(control("bar", 2), entry("bar", 2));
    assertFalse(control("foo", 1).equals(entry("foo", 2)));

<div class="screenshot">
<img src="/img/tutorial/header-param-models/image01.png">
</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] *}

Go from source and use that 'go' binary to update its source tree.

Requirements may be added, updated, and removed with 'go get'.
The vendor directory may be updated with 'go mod vendor'.
A typical sequence might be:

    cd src  # or src/cmd
    go get golang.org/x/net@master
    go mod tidy
    go mod vendor

Use caution when passing '-u' to 'go get'. The '-u' flag updates

        real-world use case so the community can discuss and debate whether this feature is actually
        the *best* way to address the real use case, or whether or not a different approach might be
        more appropriate.


        It's okay if you can't provide complete context on a use case. We understand if you are not
        able to discuss the full details of what you're working on.

      check(!closed) { "closed" }
      checkOffsetAndCount(source.size, 0, byteCount)
      socket.sink.write(source, byteCount)
    }

    override fun flush() {
      if (closed) return // Don't throw; this stream might have been closed on the caller's behalf.
      socket.sink.flush()
    }

    override fun close() {
      if (closed) return
      closed = true
      detachTimeout(timeout)

      Runnable runnable, @ParametricNullness V result) {
    return new TrustedListenableFutureTask<>(callable(runnable, result));
  }

  /*
   * In certain circumstances, this field might theoretically not be visible to an afterDone() call
   * triggered by cancel(). For details, see the comments on the fields of TimeoutFuture.
   *
   * <p>{@code volatile} is required for j2objc transpiling:

import jcifs.smb.NtlmPasswordAuthentication;

/**
 * This class is used internally by {@code NtlmHttpFilter},
 * {@code NtlmServlet}, and {@code NetworkExplorer} to negotiate password
 * hashes via NTLM SSP with MSIE. It might also be used directly by servlet
 * containers to incorporate similar functionality.
 * <p>
 * How NTLMSSP is used in conjunction with HTTP and MSIE clients is

Just functions that look the same as the *path operation functions*.

But still, it is very powerful, and allows you to declare arbitrarily deeply nested dependency "graphs" (trees).

/// tip

All this might not seem as useful with these simple examples.

But you will see how useful it is in the chapters about **security**.

And you will also see the amounts of code it will save you.

<img src="/img/tutorial/path-operation-configuration/image01.png">

### Tags with Enums { #tags-with-enums }

If you have a big application, you might end up accumulating **several tags**, and you would want to make sure you always use the **same tag** for related *path operations*.

In these cases, it could make sense to store the tags in an `Enum`.