def write_comment(self, code, text):
        """
        Write a comment record::

            writer.write_comment('PLT', 'Arrived at the first turnpoint')
            # -> LPLTArrived at the first turnpoint

        :param code: a three-letter-code describing the source of the comment
            (e.g. ``PLT`` for pilot)
        :param text: the text that should be added to the comment
        """

        if not patterns.THREE_LETTER_CODE.match(code):
            raise ValueError('Invalid source')

        self.write_record('L', code + text)