docs: def metadata_and_language_from_option_line(self, line):
          """Parse code options on the given line. When a start of a code cell
          is found, self.metadata is set to a dictionary."""
          if self.start_code_re.match(line):
              self.language, self.metadata = self.options_to_metadata(self.start_code_re.findall(line)[0])