def do_execute(self):
        """
        The actual execution of the actor.

        :return: None if successful, otherwise error message
        :rtype: str
        """
        result = None
        evl = self.input.payload
        pltclassifier.plot_classifier_errors(
            evl.predictions,
            absolute=bool(self.resolve_option("absolute")),
            max_relative_size=int(self.resolve_option("max_relative_size")),
            absolute_size=int(self.resolve_option("absolute_size")),
            title=self.resolve_option("title"),
            outfile=self.resolve_option("outfile"),
            wait=bool(self.resolve_option("wait")))
        return result