}

  // TODO(cpovirk): instead of skipping, use a smaller number of steps
  @GwtIncompatible // works but takes 5 minutes to run
  public void testPeekingIteratorBehavesLikeIteratorOnThreeElementIterable() {
    actsLikeIteratorHelper(Lists.newArrayList("A", "B", "C"));
  }

  @GwtIncompatible // works but takes 5 minutes to run
  public void testPeekingIteratorAcceptsNullElements() {

And of course, it supports the same:

* data validation
* data serialization
* data documentation, etc.

This works the same way as with Pydantic models. And it is actually achieved in the same way underneath, using Pydantic.

/// info

Keep in mind that dataclasses can't do everything Pydantic models can do.

	SHLL	CX, R12
	SHLL	CX, foo+4(SB)
	// Old syntax, still accepted:
	SHLL	CX, R11:AX // SHLL CX, AX, R11

// LTYPEM spec6	{ outcode($1, &$2); }
	MOVL	AX, R11
	MOVL	$4, R11
//	MOVL	AX, 0(AX):DS // no longer works - did it ever?

// LTYPEI spec7	{ outcode($1, &$2); }
	IMULB	DX
	IMULW	DX, BX
	IMULL	R11, R12
	IMULQ	foo+4(SB), R11

// LTYPEXC spec8	{ outcode($1, &$2); }
	CMPPD	X1, X2, 4
	CMPPD	foo+4(SB), X2, 4

    assertThat(escaper.escape("\0\uFFFF")).isEqualTo("\0\uFFFF");
  }

  public void testBuilderRetainsState() {
    // Setting a safe range and unsafe replacement works as expected.
    Escapers.Builder builder = Escapers.builder();
    builder.setSafeRange('a', 'z');
    builder.setUnsafeReplacement("X");

                                    "normal": {
                                        "summary": "A normal example",
                                        "description": "A **normal** item works correctly.",
                                        "value": {
                                            "name": "Foo",
                                            "description": "A very nice Item",

# Middleware { #middleware }

You can add middleware to **FastAPI** applications.

A "middleware" is a function that works with every **request** before it is processed by any specific *path operation*. And also with every **response** before returning it.

* It takes each **request** that comes to your application.
* It can then do something to that **request** or run any needed code.

 * {@link ValueGraph}, and {@link Network}):
 *
 * {@snippet :
 * someGraphAlgorithm(startNode, graph);
 * }
 *
 * This works because those types each implement {@code PredecessorsFunction}. It will also work
 * with any other implementation of this interface.
 *
 * <p>If you have your own graph implementation based around a custom node type {@code MyNode},

   *
   * @param pattern the pattern on which to filter file names
   */
  public PatternFilenameFilter(Pattern pattern) {
    this.pattern = Preconditions.checkNotNull(pattern);
  }

  /*
   * Our implementation works fine with a null `dir`. However, there's nothing in the documentation
   * of the supertype that suggests that implementations are expected to tolerate null. That said, I

	if err != nil {
		t.Fatalf("reading response body failed: %v", err)
	}
	if string(body) != "hello" {
		t.Fatalf("response body incorrect: %v", string(body))
	}

	// Check that Unwrap works
	if trw.Unwrap() != rw {
		t.Fatalf("Unwrap returned wrong result: %v", trw.Unwrap())
	}
}

func TestHeadersAlreadyWritten(t *testing.T) {
	rw := httptest.NewRecorder()

And an `APIRoute` subclass to use that custom request class.

### Create a custom `GzipRequest` class { #create-a-custom-gziprequest-class }

/// tip

This is a toy example to demonstrate how it works, if you need Gzip support, you can use the provided [`GzipMiddleware`](../advanced/middleware.md#gzipmiddleware){.internal-link target=_blank}.

///