code: def do_execute(self):
          
          result = None
          teeoff = True
          cond = self.storagehandler.expand(str(self.resolve_option("condition")))
          if len(cond) > 0:
              teeoff = bool(eval(cond))
          if teeoff:
              self.first_active.input = self.input
              result = self._director.execute()
          if result is None:
              self._output.append(self.input)
          return result
docs: The actual execution of the actor.
  
          :return: None if successful, otherwise error message
          :rtype: str