code: def parse_field(cls: Type[DocumentType], field_name: str, line: str) -> Any:
          
          try:
              match = cls.fields_parsers[field_name].match(line)
              if match is None:
                  raise AttributeError
              value = match.group(1)
          except AttributeError:
              raise MalformedDocumentError(field_name)
          return value
docs: Parse a document field with regular expression and return the value
  
          :param field_name: Name of the field
          :param line: Line string to parse
          :return: