code: def on_ok(self, sender):
          
          if self.remove_wfkq:
              for task in self.wfkq_tasks:
                  if task.status != task.S_OK: continue
                  children = self.wfkq_task_children[task]
                  if all(child.status == child.S_OK for child in children):
                     path = task.outdir.has_abiext("WFQ")
                     if path:
                         self.history.info("Removing WFQ: %s" % path)
                         os.remove(path)
  
          # If wfk task we create a link to a wfq file so abinit is happy
          if sender == self.wfk_task:
              wfk_path = self.wfk_task.outdir.has_abiext("WFK")
              # Check if netcdf
              filename, extension = os.path.splitext(wfk_path)
              infile = 'out_WFQ' + extension
              infile = os.path.join(os.path.dirname(wfk_path), infile)
              os.symlink(wfk_path, infile)
  
          return super().on_ok(sender)
docs: This callback is called when one task reaches status `S_OK`.
          It removes the WFKQ file if all its children have reached `S_OK`.