docs: def header(header_text: str, level: int = 1, expand_full: bool = False):
      """
      Adds a text header to the display with the specified level.
  
      :param header_text:
          The text to display in the header.
      :param level:
          The level of the header, which corresponds to the html header
          levels, such as <h1>, <h2>, ...
      :param expand_full:
          Whether or not the header will expand to fill the width of the entire
          notebook page, or be constrained by automatic maximum page width. The
          default value of False lines the header up with text displays.
      """
      r = _get_report()
      r.append_body(render.header(
          header_text,
          level=level,
          expand_full=expand_full
      ))