code: def output(self):
          
          if self._iterator is not None:
              try:
                  inst = self._iterator.next()
                  result = Token(inst)
              except Exception as e:
                  self._iterator = None
                  result = None
          else:
              result = super(LoadDataset, self).output()
          return result
docs: Returns the next available output token.
  
          :return: the next token, None if none available
          :rtype: Token