def is_multipart(header_dict):
    """
  Args:
    header_dict : CaseInsensitiveDict

  Returns:
    bool: ``True`` if ``header_dict`` has a Content-Type key (case insensitive) with
    value that begins with 'multipart'.
  """
    return (
        {k.lower(): v for k, v in header_dict.items()}
        .get("content-type", "")
        .startswith("multipart")
    )