@abc.abstractmethod<EOL><INDENT>def set_duration(self, duration):<DEDENT>
pass<EOL>
Sets the assessment duration.

        :param duration: assessment duration
        :type duration: ``osid.calendaring.Duration``
        :raise: ``InvalidArgument`` -- ``duration`` is invalid
        :raise: ``NoAccess`` -- ``Metadata.isReadOnly()`` is ``true``

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