Return the sampler and step methods current state in order to
        restart sampling at a later time.

def get_state(self):
        """
        Return the sampler and step methods current state in order to
        restart sampling at a later time.
        """

        self.step_methods = set()
        for s in self.stochastics:
            self.step_methods |= set(self.step_method_dict[s])

        state = Sampler.get_state(self)
        state['step_methods'] = {}

        # The state of each StepMethod.
        for sm in self.step_methods:
            state['step_methods'][sm._id] = sm.current_state().copy()

        return state