def visit_subscript(self, node):
        """return an astroid.Subscript node as string"""
        idx = node.slice
        if idx.__class__.__name__.lower() == "index":
            idx = idx.value
        idxstr = idx.accept(self)
        if idx.__class__.__name__.lower() == "tuple" and idx.elts:
            # Remove parenthesis in tuple and extended slice.
            # a[(::1, 1:)] is not valid syntax.
            idxstr = idxstr[1:-1]
        return "%s[%s]" % (self._precedence_parens(node, node.value), idxstr)
return an astroid.Subscript node as string