code: def _add_token_span_to_document(self, span_element):
          
          for token in span_element.text.split():
              token_id = self._add_token_to_document(token)
              if span_element.tag == 'act':  # doc can have 0+ acts
                  self._add_spanning_relation('act_{}'.format(self.act_count),
                                              token_id)
              else:  # <intro> or <conclu>
                  self._add_spanning_relation(span_element.tag, token_id)
          if span_element.tag == 'act':
              self.act_count += 1
docs: adds an <intro>, <act> or <conclu> token span to the document.