code: def _killall(self, force=False):
          
          for_termination = []
  
          for n, p in iteritems(self._processes):
              if 'returncode' not in p:
                  for_termination.append(n)
  
          for n in for_termination:
              p = self._processes[n]
              signame = 'SIGKILL' if force else 'SIGTERM'
              self._system_print("sending %s to %s (pid %s)\n" %
                                 (signame, n, p['pid']))
              if force:
                  self._env.kill(p['pid'])
              else:
                  self._env.terminate(p['pid'])
docs: Kill all remaining processes, forcefully if requested.