Parse code options on the given line. When a start of a code cell
        is found, self.metadata is set to a dictionary.

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(line[line.find('%%') + 2:])
        elif self.alternative_start_code_re.match(line):
            self.metadata = {}