If locals are provided, create a copy of self containing those
        locals in addition to what is already in this variable proxy.

def add_locals(self, locals):
        '''
        If locals are provided, create a copy of self containing those
        locals in addition to what is already in this variable proxy.
        '''
        if locals is None:
            return self
        return _jinja2_vars(self.basedir, self.vars, self.globals, locals, *self.extras)