def dont_increase_indentation(split_func: Transformer) -> Transformer:
    """Normalize prefix of the first leaf in every line returned by `split_func`.

    This is a decorator over relevant split functions.
    """

    @wraps(split_func)
    def split_wrapper(
        line: Line, features: Collection[Feature], mode: Mode
    ) -> Iterator[Line]:
        for split_line in split_func(line, features, mode):
            split_line.leaves[0].prefix = ""
            yield split_line

    return split_wrapper
Normalize prefix of the first leaf in every line returned by `split_func`.

    This is a decorator over relevant split functions.
    
src/black/linegen.py