Parses a duration string representation


        :param  representation: duration as a string, example: '1d' (day),
                                '34minutes' (minutes), '485s' (seconds)...
        :type   representation: string

        :returns: the parsed duration representation
        :rtype: DurationRepresentation

def parse(self, representation):
        """Parses a duration string representation


        :param  representation: duration as a string, example: '1d' (day),
                                '34minutes' (minutes), '485s' (seconds)...
        :type   representation: string

        :returns: the parsed duration representation
        :rtype: DurationRepresentation
        """
        elements = extract_tokens(representation)

        try:
            scales = [DurationRepresentation(float(p[0]), Scale(p[1])) for p in elements]
        except ValueError:
            raise ScaleFormatError("Malformed duration representation: {0}".format(representation))

        return scales