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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 get_xml_text(source, path=None):
 """Get the text of the XML node. If path is not None, it will get the text of the descendant of source indicated by path. """

  if path is None:
    return source.text
  else:
    return get_xml_text(get_xml_child(source, path))