code: def do_execute(self):
          
          result = None
          evl = self.input.payload
          pltclassifier.plot_prc(
              evl,
              class_index=self.resolve_option("class_index"),
              title=self.resolve_option("title"),
              key_loc=self.resolve_option("key_loc"),
              outfile=self.resolve_option("outfile"),
              wait=bool(self.resolve_option("wait")))
          return result
docs: The actual execution of the actor.
  
          :return: None if successful, otherwise error message
          :rtype: str