@abc.abstractmethod<EOL><INDENT>def get_key_resource_id(self):<DEDENT>
return<EOL>
Gets the ``Id`` of the key resource of this entry.

        The key resource may be a student or other applicable key to
        identify a row of grading entries.

        :return: ``Id`` of the key resource
        :rtype: ``osid.id.Id``


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