docs: def gen_ordered(self):
          """Generate batches of operations, batched by type of
          operation, in the order **provided**.
          """
          run = None
          for idx, (op_type, operation) in enumerate(self.ops):
              if run is None:
                  run = _Run(op_type)
              elif run.op_type != op_type:
                  yield run
                  run = _Run(op_type)
              run.add(idx, operation)
          yield run