def clear_value(self, ctx):
        node_state = self._get_state(ctx)
        node_state.has_value = False
        node_state.value = None
        node_state.generator = None

        # clearing the value also marks the node as dirty
        self._set_dirty(node_state, DIRTY_FLAGS_ALL, 0)
Removes the content of responses for HEAD requests, 1xx, 204 and 304
dataset/ETHPy150Open manahl/mdf/mdf/nodes.py/MDFNode.clear_value--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/http/utils.py/conditional_content_removal