And Pydantic's `Field` returns an instance of `FieldInfo` as well.

`Body` also returns objects of a subclass of `FieldInfo` directly. And there are others you will see later that are subclasses of the `Body` class.

Remember that when you import `Query`, `Path`, and others from `fastapi`, those are actually functions that return special classes.

///

/// tip

     * @throws IOException if an I/O error occurs
     */
    @Override
    public int read(final byte[] b, final int off, final int len) throws IOException {
        return inputStream.read(b, off, len);
    }

    /**
     * Reads some number of bytes from the input stream and stores them into the buffer array b.
     *

But you also want it to accept new items. And when the items didn't exist before, it creates them, and returns an HTTP status code of 201 "Created".

To achieve that, import `JSONResponse`, and return your content there directly, setting the `status_code` that you want:

{* ../../docs_src/additional_status_codes/tutorial001_an_py310.py hl[4,25] *}

/// warning

import org.jspecify.annotations.Nullable;

/**
 * To be implemented by test generators of things that can contain elements. Such things include
 * both {@link Collection} and {@link Map}; since there isn't an established collective noun that
 * encompasses both of these, 'container' is used.
 *
 * @author George van den Driessche
 */
@GwtCompatible
@NullMarked
public interface TestContainerGenerator<T, E extends @Nullable Object> {

   * suppression externally, but it's OK because we don't enforce test-size rules there.)
   *
   * We'd just use PackageSanityTests directly, saving us from needing this separate type, but we're
   * currently skipping MediumTests on Android, and we skip them by not making them present at
   * runtime at all. I could just make _this_ test a MediumTest, but then it wouldn't run on

        : SetTestSuiteBuilder.using(keySetGenerator);
  }

  /**
   * To avoid infinite recursion, test suites with these marker features won't have derived suites
   * created for them.
   */
  enum NoRecurse implements Feature<@Nullable Void> {
    SUBMAP,
    DESCENDING;

    @Override
    public Set<Feature<? super @Nullable Void>> getImpliedFeatures() {

  // null pointer. If `table[h] == 0` that means there are no keys in the map whose short hash is h.
  // If the `next` bits in `entries[i]` are 0 that means there are no further entries for the given
  // short hash. But 0 is also a valid index in `entries`, so we add 1 to these indices before
  // putting them in `table` or in `next` bits, and subtract 1 again when we need an index value.
  //

 *   <li>When there are no URLs in the queue ({@link #delayAtNoUrlInQueue()})</li>
 *   <li>While waiting for new URLs to be added to the queue ({@link #delayForWaitingNewUrl()})</li>
 * </ul>
 *
 * <p>
 * Subclasses are responsible for implementing the abstract methods to define the actual delay
 * mechanism for each of these stages.
 * </p>
 *
 * <p>

existing object replication are not marked as `PENDING` prior to replication.

While there are competing ways to represent absence (`Optional`, "Null Object" pattern, method overloads),
it is unlikely that we'll be able to remove `null` entirely.

After migrating to Java 8, we can use pluggable type checkers to ensure that our annotations are consistent, 
and there are no missing null checks.

## Decision