# sn_basis/functions/ly_existence_wrapper.py

def layer_exists(layer) -> bool:
    if layer is None:
        return False

    is_valid_flag = getattr(layer, "is_valid", None)
    if is_valid_flag is not None:
        try:
            return bool(is_valid_flag)
        except Exception:
            return False

    try:
        is_valid = getattr(layer, "isValid", None)
        if callable(is_valid):
            return bool(is_valid())
        return True
    except Exception:
        return False