docs: def gen_unordered(self):
          """Generate batches of operations, batched by type of
          operation, in arbitrary order.
          """
          operations = [_Run(_INSERT), _Run(_UPDATE), _Run(_DELETE)]
          for idx, (op_type, operation) in enumerate(self.ops):
              operations[op_type].add(idx, operation)
  
          for run in operations:
              if run.ops:
                  yield run