code: def get_cur_batch(items):
      
      batches = []
      for data in items:
          batch = tz.get_in(["metadata", "batch"], data, [])
          batches.append(set(batch) if isinstance(batch, (list, tuple)) else set([batch]))
      combo_batches = reduce(lambda b1, b2: b1.intersection(b2), batches)
      if len(combo_batches) == 1:
          return combo_batches.pop()
      elif len(combo_batches) == 0:
          return None
      else:
          raise ValueError("Found multiple overlapping batches: %s -- %s" % (combo_batches, batches))
docs: Retrieve name of the batch shared between all items in a group.