a.internal-link::after {
  /* \00A0 is a non-breaking space
        to make the mark be on the same line as the link
    */
  content: "\00A0↪";
}

.shadow {
  box-shadow: 5px 5px 10px #999;
}

/* Give space to lower icons so Gitter chat doesn't get on top of them */
.md-footer-meta {
  padding-bottom: 2em;
}

.user-list {
  display: flex;
  flex-wrap: wrap;
  margin-bottom: 2rem;
}

* Convert the corresponding types (if needed).
* Validate the data.
    * If the data is invalid, it will return a nice and clear error, indicating exactly where and what was the incorrect data.
* Give you the received data in the parameter `item`.
    * As you declared it in the function to be of type `Item`, you will also have all the editor support (completion, etc) for all of the attributes and their types.

    val charset = parameter("charset") ?: return defaultValue
    return try {
      Charset.forName(charset)
    } catch (_: IllegalArgumentException) {
      defaultValue // This charset is invalid or unsupported. Give up.
    }
  }

  /**
   * Returns the parameter [name] of this media type, or null if this media type does not define
   * such a parameter.
   */
  fun parameter(name: String): String? = commonParameter(name)

        return (null == hint
                ? getLoggerForComponent(role)
                : new Slf4jLogger(loggerFactory.getLogger(role + '.' + hint)));
    }

    //
    // Trying to give loggers back is a bad idea. Ceki said so :-)
    // notice to self: what was this method supposed to do?
    //
    /**
     * <b>Warning</b>: ignored.
     */
    public void returnComponentLogger(String role) {}

  // to the given dividend, so that we don't have half of our divisions being
  // trivial because the divisor is bigger than the dividend.
  // Using remainder here does not give us a uniform distribution but it should
  // not have a big impact on the measurement.
  private static long randomDivisor(long dividend) {
    long r = RANDOM_SOURCE.nextLong();
    if (dividend == -1) {
      return r;

 |
 |                 NOTE: This location can be overridden with the CLI option:
 |
 |                 -it /path/to/installation/toolchains.xml
 |
 | The sections in this sample file are intended to give you a running start at
 | getting the most out of your Maven installation.
 |-->
<toolchains xmlns="http://maven.apache.org/TOOLCHAINS/1.1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

  // For example: (long) data[i++] | (long) data[i++] << 8 | ...
  // If data[i] == (byte) 0x80, the first cast will sign-extend it to 0xffffffffffffff80,
  // masking the remaining seven bytes.
  // To test this, we give an input where bit 7 is not cleared. For example:
  // (1) 00 01 02 03 04 05 06 07 80
  // (2) 00 01 02 03 04 05 06 07 81
  // (3) 00 01 02 03 04 05 06 07 ff (or anything in between)

  // For example: (long) data[i++] | (long) data[i++] << 8 | ...
  // If data[i] == (byte) 0x80, the first cast will sign-extend it to 0xffffffffffffff80,
  // masking the remaining seven bytes.
  // To test this, we give an input where bit 7 is not cleared. For example:
  // (1) 00 01 02 03 04 05 06 07 80
  // (2) 00 01 02 03 04 05 06 07 81
  // (3) 00 01 02 03 04 05 06 07 ff (or anything in between)

  private ClassToInstanceMap<Number> map;

  @Override
  protected void setUp() throws Exception {
    map = MutableClassToInstanceMap.create();
  }

  public void testConstraint() {

    /**
     * We'll give ourselves a pass on testing all the possible ways of breaking the constraint,
     * because we know that newClassMap() is implemented using ConstrainedMap which is itself

///

```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">
<img src="/img/tutorial/header-param-models/image01.png">
</div>