code: def stop_ppp_link(self):
          '''stop the link'''
          if self.ppp_fd == -1:
              return
          try:
              self.mpself.select_extra.pop(self.ppp_fd)
              os.close(self.ppp_fd)
              os.waitpid(self.pid, 0)
          except Exception:
              pass
          self.pid = -1
          self.ppp_fd = -1
          print("stopped ppp link"f stop_ppp_link(self):
          '''stop the link'''
          if self.ppp_fd == -1:
              return
          try:
              self.mpself.select_extra.pop(self.ppp_fd)
              os.close(self.ppp_fd)
              os.waitpid(self.pid, 0)
          except Exception:
              pass
          self.pid = -1
          self.ppp_fd = -1
          print("stopped ppp link")
docs: stop the link