code: def pad_dialogues(self, dialogues):
                  
          self.log('info', 'Padding the dialogues ...')
          
          return [self.pad_dialogue(d) for d in dialogues]
docs: Pad the entire dataset.
          This involves adding padding at the end of each sentence, and in the case of
          a hierarchical model, it also involves adding padding at the end of each dialogue,
          so that every training sample (dialogue) has the same dimension.