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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 parse_xml_file(self, fileobj, id_generator=None):
 """Parse an open XML file, returning a usage id."""

        root = etree.parse(fileobj).getroot()
        usage_id = self._usage_id_from_node(root, None, id_generator)
        return usage_id