Prefer to use the `Annotated` version if possible.

///

```Python hl_lines="7-12  16"
{!> ../../docs_src/header_param_models/tutorial001_py310.py!}
```

////

**FastAPI** will **extract** the data for **each field** from the **headers** in the request and give you the Pydantic model you defined.

## Check the Docs

You can see the required headers in the docs UI at `/docs`:

<div class="screenshot">

                  public Integer load(Integer from) {
                    return (int) misses.incrementAndGet();
                  }
                });

    // To start, fill up the cache.
    // Each miss both increments the counter and causes the map to grow by one,
    // so until evictions begin, the size of the map is the greatest return
    // value seen so far
    while (cache.getUnchecked(nextRandomKey()) < maximumSize) {}

      long result = 1;
      for (int i = n1 + 1; i <= n2; i++) {
        result *= i;
      }
      return BigInteger.valueOf(result);
    }

    /*
     * We want each multiplication to have both sides with approximately the same number of digits.
     * Currently, we just divide the range in half.
     */
    int mid = (n1 + n2) >>> 1;

 *
 * @author Kurt Alfred Kluever
 */
@Immutable
@ElementTypesAreNonnullByDefault
final class MacHashFunction extends AbstractHashFunction {

  @SuppressWarnings("Immutable") // cloned before each use
  private final Mac prototype;

  @SuppressWarnings("Immutable") // keys are immutable, but not provably so
  private final Key key;

  private final String toString;
  private final int bits;

   * escapes only the following five ASCII characters: {@code '"&<>}.
   */
  public static Escaper htmlEscaper() {
    return HTML_ESCAPER;
  }

  // For each xxxEscaper() method, please add links to external reference pages
  // that are considered authoritative for the behavior of that escaper.

  private static final Escaper HTML_ESCAPER =
      Escapers.builder()

   * weak, or phantom references.
   *
   * @param backingMap place to store the mapping from each row key to its corresponding column key
   *     / value map
   * @param factory supplier of new, empty maps that will each hold all column key / value mappings
   *     for a given row key
   * @throws IllegalArgumentException if {@code backingMap} is not empty
   * @since 10.0

import org.junit.jupiter.api.Test

/**
 * Unit test for [FastFallbackExchangeFinder] implementation details.
 *
 * This test uses [TaskFaker] to deterministically test racy code. Each function in this test has
 * the same structure:
 *
 *  * prepare a set of plans, each with a predictable connect delay
 *  * attempt to find a connection
 *  * step through time, asserting that the expected side effects are performed.
 */

    }
    Object result;
    try {
      result = supplier.get();
    } catch (Throwable t) {
      if (predicate.apply(t)) {
        // We are careful to set up INSTANCE_OF to match each Predicate to its target Class.
        @SuppressWarnings("unchecked")
        T caught = (T) t;
        return caught;
      }
      throw new AssertionError(

 *   <dt>{@link SetMultimap}
 *   <dd>An extension of {@link Multimap} which has order-independent equality and does not allow
 *       duplicate entries; that is, while a key may appear twice in a {@code SetMultimap}, each
 *       must map to a different value. {@code SetMultimap} takes its name from the fact that the
 *       {@linkplain SetMultimap#get collection of values} associated with a given key fulfills the

    }

    CacheTesting.processPendingNotifications(cache);
    assertEquals(1, cache.size());
    assertEquals(1, removalListener.getCount());
  }

  // A simple type whose .toString() will return the same value each time, but without maintaining
  // a strong reference to that value.
  static class Key {
    private final int value;
    private WeakReference<String> toString;

    Key(int value) {
      this.value = value;