Method _add_fetch_ops

python/paddle/base/executor.py:2785–2821

(
        cls, program, fetch_list, fetch_var_name, use_fetch_v2=False
    )

    @classmethod
    def _add_fetch_ops(
        cls, program, fetch_list, fetch_var_name, use_fetch_v2=False
    ):
        tmp_program = program.clone()

        global_block = tmp_program.global_block()

        if fetch_var_name in global_block.vars:
            fetch_var = global_block.var(fetch_var_name)
        else:
            fetch_var = global_block.create_var(
                name=fetch_var_name,
                type=core.VarDesc.VarType.FETCH_LIST,
                persistable=True,
            )

        if use_fetch_v2:
            fetch_op = 'fetch_v2'
        else:
            fetch_op = 'fetch'

        # append fetch_operators
        if not has_fetch_operators(
            global_block, fetch_list, fetch_var_name, fetch_op
        ):
            for i, var in enumerate(fetch_list):
                assert isinstance(var, (Variable, str)), (
                    f"Wrong type for fetch_list[{i}]: {type(var)}"
                )
                global_block.append_op(
                    type=fetch_op,
                    inputs={'X': [var]},
                    outputs={'Out': [fetch_var]},
                    attrs={'col': i},
                )

        return tmp_program

    @classmethod
    def _remove_fetch_ops(cls, program, fetch_op_name='fetch'):