code: def haslayer(self, cls):
          
          if cls == "NTP":
              if isinstance(self, NTP):
                  return True
          elif issubtype(cls, NTP):
              if isinstance(self, cls):
                  return True
          return super(NTP, self).haslayer(cls)
docs: Specific: NTPHeader().haslayer(NTP) should return True.