code: def coreferences(self):
          
          if self._coreferences is None:
              coreferences = self._xml.xpath('/root/document/coreference/coreference')
              if len(coreferences) > 0:
                  self._coreferences = [Coreference(self, element) for element in coreferences]
          return self._coreferences
docs: Returns a list of Coreference classes
  
          :getter: Returns a list of coreferences
          :type: list of corenlp_xml.coreference.Coreference