def visit_unaryop(self, node):
        """`not len(S)` must become `not S` regardless if the parent block
        is a test condition or something else (boolean expression)
        e.g. `if not len(S):`"""
        if (
            isinstance(node, astroid.UnaryOp)
            and node.op == "not"
            and _is_len_call(node.operand)
        ):
            self.add_message("len-as-condition", node=node)
`not len(S)` must become `not S` regardless if the parent block
        is a test condition or something else (boolean expression)
        e.g. `if not len(S):`