mypy

dc325e41 - Fix internal error inheriting a dataclass duplicated field #7792 (#7808)

Fix internal error inheriting a dataclass duplicated field #7792 (#7808) The error was: ``` (attr,) = [a for a in all_attrs if a.name == name] ValueError: not enough values to unpack (expected 1, got 0) ``` No need to enter in the `else` if all_attrs is empty And don't assume that there is a matching attr in all_attr