code: def _get_all_offsets(self, offset_ns=None):
          
          for token_id, _token_str in self.get_tokens():
              onset = self.node[token_id]['{0}:{1}'.format(offset_ns, 'onset')]
              offset = self.node[token_id]['{0}:{1}'.format(offset_ns, 'offset')]
              yield (token_id, onset, offset)
docs: returns all token offsets of this document as a generator of
          (token node ID str, character onset int, character offset int) tuples.
  
          Parameters
          ----------
          offset_ns : str or None
              The namespace from which the offsets will be retrieved. If no
              namespace is given, the default namespace of this document graph is
              chosen
  
          Returns
          -------
          offsets : generator(tuple(str, int, int))
              a generator of (token node ID str, character onset int, character
              offset int) tuples, which represents all the tokens in the order
              they occur in the document.