{* ../../docs_src/request_form_models/tutorial001_an_py310.py hl[9:11,15] *}

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

## Check the Docs { #check-the-docs }

You can verify it in the docs UI at `/docs`:

            """
        ),
    ] = _Unset,
    alias: Annotated[
        str | None,
        Doc(
            """
            An alternative name for the parameter field.

            This will be used to extract the data and for the generated OpenAPI.
            It is particularly useful when you can't use the name you want because it
            is a Python reserved keyword or similar.
            """
        ),
    ] = None,

    }

    /**
     * Extracts the virtual host key from a RelatedQuery entity.
     * If the virtual host is blank or null, returns an empty string.
     *
     * @param entity the RelatedQuery entity to extract the host key from
     * @return the virtual host key, or empty string if blank or null
     */
    protected String getHostKey(final RelatedQuery entity) {
        final String key = entity.getVirtualHost();

Declare the **header parameters** that you need in a **Pydantic model**, and then declare the parameter as `Header`:

{* ../../docs_src/header_param_models/tutorial001_an_py310.py hl[9:14,18] *}

**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 { #check-the-docs }

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

        }
        String url = distributionUrl.substring(idx + 1).trim();

        Matcher m = WRAPPER_VERSION_EXTRACT.matcher(url);
        if (!m.matches()) {
            throw new IllegalStateException("Could not extract wrapper version from distributionUrl: " + url);
        }
        return m.group(1);
    }

    private static void run(String... cmd) throws IOException, InterruptedException, ExecutionException {

      try {
        return extract();
      } finally {
        monitor.leave();
      }
    } else {
      return null;
    }
  }

  @CanIgnoreReturnValue
  @Override
  public E take() throws InterruptedException {
    Monitor monitor = this.monitor;
    monitor.enterWhen(notEmpty);
    try {
      return extract();
    } finally {
      monitor.leave();
    }

    // Trace the operation now (create a node in the graph).
    TF_ExecuteOperation(add_op, 2, inputs, add_outputs, s);
    ASSERT_EQ(TF_OK, TF_GetCode(s)) << TF_Message(s);
    TF_DeleteAbstractOp(add_op);
    // Extract the resulting tensor.
    add_output1 = TF_OutputListGet(add_outputs, 0);
    TF_DeleteOutputList(add_outputs);
  }

  // Same with a second "Add" computing `arg1 + arg1`.
  TF_AbstractTensor* add_output2;
  {

     * Gets the appropriate extractor for the given response data.
     * Selects an extractor based on the MIME type or falls back to the Tika extractor.
     *
     * @param responseData the response data containing the document to extract
     * @return the extractor instance for processing the document
     * @throws FessSystemException if no suitable extractor can be found
     */
    @Override

        with:
          name: maven-distributions
          path: maven-dist

      - name: List downloaded files
        shell: bash
        run: ls -la maven-dist

      - name: Extract Maven distribution
        shell: bash
        run: |
          mkdir -p maven-local
          if [ "${{ runner.os }}" = "Windows" ]; then
            unzip maven-dist/apache-maven-*-bin.zip -d maven-local

But a variable like `user-agent` is invalid in Python.

So, by default, `Header` will convert the parameter names characters from underscore (`_`) to hyphen (`-`) to extract and document the headers.

Also, HTTP headers are case-insensitive, so, you can declare them with standard Python style (also known as "snake_case").