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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 add_electrode(self, electrode, label=None):
 """ Add an electrode to the plot. Args: electrode: An electrode. All electrodes satisfying the AbstractElectrode interface should work. label: A label for the electrode. If None, defaults to a counting """

        if not label:
            label = "Electrode {}".format(len(self._electrodes) + 1)
        self._electrodes[label] = electrode