@abc.abstractmethod<EOL><INDENT>def get_activity_form_for_update(self, activity_id):<DEDENT>
return<EOL>
Gets the activity form for updating an existing activity.

        A new activity form should be requested for each update
        transaction.

        :param activity_id: the ``Id`` of the ``Activity``
        :type activity_id: ``osid.id.Id``
        :return: the activity form
        :rtype: ``osid.learning.ActivityForm``
        :raise: ``NotFound`` -- ``activity_id`` is not found
        :raise: ``NullArgument`` -- ``activity_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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