code: def writePIDFile(self):
          
          with self._jobStore.writeSharedFileStream('pid.log') as f:
              f.write(str(os.getpid()).encode('utf-8'))
docs: Write a the pid of this process to a file in the jobstore.
  
          Overwriting the current contents of pid.log is a feature, not a bug of this method.
          Other methods will rely on always having the most current pid available.
          So far there is no reason to store any old pids.