Update import context using overwriting name information.

        Examples
        --------
        >> import foo
        >> import bar
        >> def foo(bar):
        >>     print(bar)

        In this case, neither bar nor foo can be used in the foo function and
        in future function, foo will not be usable.

def visit_FunctionDef(self, node):
        """
        Update import context using overwriting name information.

        Examples
        --------
        >> import foo
        >> import bar
        >> def foo(bar):
        >>     print(bar)

        In this case, neither bar nor foo can be used in the foo function and
        in future function, foo will not be usable.
        """
        self.symbols.pop(node.name, None)
        gsymbols = self.symbols.copy()
        [self.symbols.pop(arg.id, None) for arg in node.args.args]
        self.generic_visit(node)
        self.symbols = gsymbols
        return node