code: def append_provenance_step(self, title, description, timestamp=None):
          
          step_time = self._provenance.append_step(title, description, timestamp)
          if step_time > self.last_update:
              self.last_update = step_time
docs: Add a step to the provenance of the metadata
  
          :param title: The title of the step.
          :type title: str
  
          :param description: The content of the step
          :type description: str
  
          :param timestamp: the time of the step
          :type timestamp: datetime, str