code: def reject_batch(self):
          
          prev_size = 0
          if len(self.un_committed) == 0:
              raise LogicError("No items to return")
          if len(self.un_committed) > 0:
              _, _, prev_size = self.un_committed.pop()
          if len(self.un_committed) == 0:
              committed_hash, committed_root, committed_size = self.last_committed
              return committed_hash, committed_root, prev_size - committed_size
          else:
              lhash, ltxn_root, lsize = self.un_committed[-1]
              return lhash, ltxn_root, prev_size - lsize
docs: Return hash reverting for and calculate count of reverted txns
          :return: root_hash, for reverting to (needed in revertToHead method) and count of reverted txns