code: def _set_least_batch_id(self, txn_signature):
          
  
          batch = self._batches_by_txn_id[txn_signature]
  
          least_index = self._index_of_batch(
              self._batches_by_id[self._least_batch_id_wo_results].batch)
  
          current_index = self._index_of_batch(batch)
          all_prior = False
  
          if current_index <= least_index:
              return
              # Test to see if all batches from the least_batch to
              # the prior batch to the current batch have results.
          if all(
                  all(t.header_signature in self._txn_results
                      for t in b.transactions)
                  for b in self._batches[least_index:current_index]):
              all_prior = True
          if not all_prior:
              return
          possible_least = self._batches[current_index].header_signature
          # Find the first batch from the current batch on, that doesn't have
          # all results.
          for b in self._batches[current_index:]:
              if not all(t.header_signature in self._txn_results
                         for t in b.transactions):
                  possible_least = b.header_signature
                  break
          self._least_batch_id_wo_results = possible_least
docs: Set the first batch id that doesn't have all results.
  
          Args:
              txn_signature (str): The txn identifier of the transaction with
                  results being set.