code: def _remove_batches(self, block, keep_batches):
          
          clone = Block()
          clone.header = block.header
          clone.header_signature = block.header_signature
          clone.batches.extend([
              batch for batch in block.batches
              if batch.header_signature in keep_batches
          ])
          return clone
docs: Returns a copy of the block without the non-injected
          batches, which other validators are likely to already
          have. This reduces the size of the broadcasted block.