def get_duration(self):
<EOL>if not bool(self._my_map['<STR_LIT>']):<EOL><INDENT>raise errors.IllegalState()<EOL><DEDENT>return Duration(**self._my_map['<STR_LIT>'])<EOL>
Gets the duration for this assessment.

        return: (osid.calendaring.Duration) - the duration
        raise:  IllegalState - ``has_duration()`` is ``false``
        *compliance: mandatory -- This method must be implemented.*