@abc.abstractmethod<EOL><INDENT>def has_fixed_start_offset(self):<DEDENT>
return<EOL>
Tests if this offset start time based on a fixed period of time.

        :return: ``true`` if this offset is based on a fixed period of time, ``false`` otherwise
        :rtype: ``boolean``
        :raise: ``IllegalState`` -- ``has_fixed_start_time()`` is ``true``

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