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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 add_node_as_child(self, block, node, id_generator=None):
 """ Called by XBlock.parse_xml to treat a child node as a child block. """

        usage_id = self._usage_id_from_node(node, block.scope_ids.usage_id, id_generator)
        block.children.append(usage_id)