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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_gradebook_column_gradebook_session(self):
 """Gets the session for retrieving gradebook column to gradebook mappings. return: (osid.grading.GradebookColumnGradebookSession) - a ``GradebookColumnGradebookSession`` raise: OperationFailed - unable to complete request raise: Unimplemented - ``supports_gradebook_column_gradebook()`` is ``false`` *compliance: optional -- This method must be implemented if ``supports_gradebook_column_gradebook()`` is ``true``.* """

        if not self.supports_gradebook_column_gradebook():
            raise errors.Unimplemented()
        # pylint: disable=no-member
        return sessions.GradebookColumnGradebookSession(runtime=self._runtime)