docs: def c14n(xml):
      '''
      Applies c14n to the xml input
      @param xml: str
      @return: str
      '''
      tree = etree.parse(StringIO(xml))
      output = StringIO()
      tree.write_c14n(output, exclusive=False, with_comments=True, compression=0)
      output.flush()
      c14nized = output.getvalue()
      output.close()
      return c14nized