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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 plot(self, entity):
 """ Basic plot of a single binary sensor data. Parameters entity : string The entity to plot """

        df = self._binary_df[[entity]]
        resampled = df.resample("s").ffill()  # Sample at seconds and ffill
        resampled.columns = ["value"]
        fig, ax = plt.subplots(1, 1, figsize=(16, 2))
        ax.fill_between(resampled.index, y1=0, y2=1, facecolor="royalblue", label="off")
        ax.fill_between(
            resampled.index,
            y1=0,
            y2=1,
            where=(resampled["value"] > 0),
            facecolor="red",
            label="on",
        )
        ax.set_title(entity)
        ax.set_xlabel("Date")
        ax.set_frame_on(False)
        ax.set_yticks([])
        plt.legend(loc=(1.01, 0.7))
        plt.show()
        return