code: def get_cgi_parameter_bool_or_none(form: cgi.FieldStorage,
                                     key: str) -> Optional[bool]:
      
      return get_cgi_parameter_bool_or_default(form, key, default=None)
docs: Extracts a boolean parameter from a CGI form (``"1"`` = ``True``,
      other string = False, absent/zero-length string = ``None``).