code: def run(self):
          
          flag = True
          if self._exeng == 'dpkt':
              flag, engine = self.import_test('dpkt', name='DPKT')
              if flag:
                  return self._run_dpkt(engine)
          elif self._exeng == 'scapy':
              flag, engine = self.import_test('scapy.all', name='Scapy')
              if flag:
                  return self._run_scapy(engine)
          elif self._exeng == 'pyshark':
              flag, engine = self.import_test('pyshark', name='PyShark')
              if flag:
                  return self._run_pyshark(engine)
          elif self._exeng == 'pipeline':
              flag, engine = self.import_test('multiprocessing', name='Pipeline Multiprocessing')
              self._flag_m = flag = bool(flag and (self._flag_a and CPU_CNT > 1))
              if self._flag_m:
                  return self._run_pipeline(engine)
              warnings.warn(f'extraction engine Pipeline Multiprocessing is not available; '
                            'using default engine instead', EngineWarning, stacklevel=stacklevel())
          elif self._exeng == 'server':
              flag, engine = self.import_test('multiprocessing', name='Server Multiprocessing')
              self._flag_m = flag = bool(flag and (self._flag_a and CPU_CNT > 2))
              if self._flag_m:
                  return self._run_server(engine)
              warnings.warn(f'extraction engine Server Multiprocessing is not available; '
                            'using default engine instead', EngineWarning, stacklevel=stacklevel())
          elif self._exeng not in ('default', 'pcapkit'):
              flag = False
              warnings.warn(f'unsupported extraction engine: {self._exeng}; '
                            'using default engine instead', EngineWarning, stacklevel=stacklevel())
  
          # using default/pcapkit engine
          self._exeng = self._exeng if flag else 'default'
          self.record_header()            # read PCAP global header
          self.record_frames()
docs: Start extraction.