Returns `<data_var>["<name>"]`

def __get_subscript(self, name, ctx=None):
    """
    Returns `<data_var>["<name>"]`
    """

    assert isinstance(name, string_types), name
    return ast.Subscript(
      value=ast.Name(id=self.data_var, ctx=ast.Load()),
      slice=ast.Index(value=ast.Str(s=name)),
      ctx=ctx)