Return the string as it should be presented in a MapChart
        input file.

def to_string(self):
        """ Return the string as it should be presented in a MapChart
        input file.

        """
        return '%s   %s %s %s %s' % (
            self.trait, self.start_position, self.peak_start_position,
            self.peak_stop_position, self.stop_position)