code: def _read_frame(self):
          
          if self._exeng == 'scapy':
              return self._scapy_read_frame()
          elif self._exeng == 'dpkt':
              return self._dpkt_read_frame()
          elif self._exeng == 'pyshark':
              return self._pyshark_read_frame()
          else:
              return self._default_read_frame()
docs: Headquarters for frame reader.