* such custom interfaces directly; they are implemented only in subclasses. Therefore, forwarding
 * {@code equals} would break symmetry, as the forwarding object might consider itself equal to the
 * object being tested, but the reverse could not be true. This behavior is consistent with the
 * JDK's collection wrappers, such as {@link java.util.Collections#unmodifiableCollection}. Use an

 *       href="https://github.com/google/guava/issues/6126#issuecomment-1204399671">treats it
 *       identically to {@code Nullable}</a> as of version 0.9.9.
 *   <li><a href="https://developers.google.com/j2objc">J2ObjC</a>, maybe: It might no longer be
 *       necessary there, since we have stopped using the {@code @ParametersAreNonnullByDefault}
 *       annotations that {@code ParametricNullness} was counteracting.
 * </ul>
 *

    this.iterator = iterator;
  }

  @Override
  public Iterator<E> iterator() {
    if (iterator == null) {
      // TODO: throw something else? Do we worry that people's code and tests
      // might be relying on this particular type of exception?
      throw new IllegalStateException();
    }
    try {
      return iterator;
    } finally {
      iterator = null;
    }
  }

/// tip

Some editors check for unused function parameters, and show them as errors.

Using these `dependencies` in the *path operation decorator* you can make sure they are executed while avoiding editor/tooling errors.

It might also help avoid confusion for new developers that see an unused parameter in your code and could think it's unnecessary.

///

/// info

In this example we use invented custom headers `X-Key` and `X-Token`.

#!/usr/bin/env bash
#
# Copyright 2022 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,

            "The system cannot find the file specified.", "Bad password.", "The system cannot find the path specified.", "reserved",
            "The client does not have the necessary access rights to perform the requested function.", "Access is denied.",
            "The TID specified was invalid.", "The handle is invalid.", "The network name cannot be found.",

            "The system cannot find the file specified.", "Bad password.", "The system cannot find the path specified.", "reserved",
            "The client does not have the necessary access rights to perform the requested function.", "Access is denied.",
            "The TID specified was invalid.", "The handle is invalid.", "The network name cannot be found.",

     */
    @Test
    void testToString() {
        // The actual toString() method uses super.toString(), so we mimic that for the check.
        // A direct string comparison might be brittle, so we check for the class name and brackets.
        String actualString = response.toString();
        assertTrue(actualString.startsWith("Trans2SetFileInformationResponse["),

        try {
            String[] languages = searchHelper.getLanguages(getMockRequest(), params);

            assertNotNull(languages);
            if (languages.length > 0) {
                // Note: The actual order might be different due to normalization
                boolean hasEn = false, hasJa = false;
                for (String lang : languages) {
                    if ("en".equals(lang))
                        hasEn = true;

The whole **FastAPI** framework is based to satisfy that. Autocompletion works everywhere.

You will rarely need to come back to the docs.

Here's how your editor might help you:

* in <a href="https://code.visualstudio.com/" class="external-link" target="_blank">Visual Studio Code</a>:

![editor support](https://fastapi.tiangolo.com/img/vscode-completion.png)