code: def xpath(source_xml, xpath_expr, req_format='string'):
      tree = source_xml
      if not isinstance(source_xml, ET.Element):
          tree = objectify.fromstring(source_xml)
      for elem in tree.getiterator():
          if isinstance(elem.tag, basestring):
              i = elem.tag.find('}')
              if i >= 0:
                  elem.tag = elem.tag[i+1:]
      objectify.deannotate(tree, cleanup_namespaces=True)
      filtered_list = tree.xpath(xpath_expr)
      if req_format == 'xml':
          return filtered_list
      matches = ''.join(etree.tostring(
          element, pretty_print=True) for element in filtered_list)
      return matches if matches else ""