@abc.abstractmethod<EOL><INDENT>def has_time_period(self):<DEDENT>
return<EOL>
Tests if a ``TimePeriod`` is associated with this schedule.

        The time period determines the start and end time of the
        recurring series.

        :return: ``true`` if there is an associated ``TimePeriod,``  ``false`` otherwise
        :rtype: ``boolean``


        *compliance: mandatory -- This method must be implemented.*