def _add_scope(self, s, fl=0):
        print "adding scope %s" % s.name
        s.fl = fl
        self._assign_variablesReference(s)
        self._scopes += [s]
        for c in s.children:
            c.scope = s
            self._add_variables_references(c)
        if not fl in self._known_frame_levels:
            self._known_frame_levels += [fl]