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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def show(self):
 """ Plot the result of the simulation once it's been intialized """


        from matplotlib import pyplot as plt

        if self.already_run:
            
            for ref in self.volts.keys():

                plt.plot(self.t, self.volts[ref], label=ref)
                plt.title("Simulation voltage vs time")
                plt.legend()
                plt.xlabel("Time [ms]")
                plt.ylabel("Voltage [mV]")

        else:
            pynml.print_comment("First you have to 'go()' the simulation.", True)
        plt.show()