code: def _conversations(group, delta=datetime.timedelta(hours=1)):
      last_time = None
      results = []
      for g in group:
          if last_time is None or g.datetime - last_time < delta:
              if g.interaction == 'text':
                  results.append(g)
              else:
                  if len(results) != 0:
                      yield results
                      results = []
          else:
              if len(results) != 0:
                  yield results
              if g.interaction == 'call':
                  results = []
              else:
                  results = [g]
          last_time = g.datetime
      if len(results) != 0:
          yield results