code: def p_open_mixin(self, p):
          
          p[1].parse(self.scope)
          self.scope.current = p[1]
          p[0] = [p[1], p[3]]
          if len(p) > 6:
              p[0].append(p[5])
          else:
              p[0].append(None)
docs: open_mixin                : identifier t_popen mixin_args_list t_pclose brace_open
                                        | identifier t_popen mixin_args_list t_pclose mixin_guard brace_open