docs: def get_book_admin_session(self, proxy):
          """Gets the ``OsidSession`` associated with the book administrative service.
  
          arg:    proxy (osid.proxy.Proxy): a proxy
          return: (osid.commenting.BookAdminSession) - a
                  ``BookAdminSession``
          raise:  NullArgument - ``proxy`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  Unimplemented - ``supports_book_admin()`` is ``false``
          *compliance: optional -- This method must be implemented if
          ``supports_book_admin()`` is ``true``.*
  
          """
          if not self.supports_book_admin():
              raise errors.Unimplemented()
          # pylint: disable=no-member
          return sessions.BookAdminSession(proxy=proxy, runtime=self._runtime)