def plot_histogram(self, ax: plt.Axes | None = None, **plot_kwargs) -> plt.Axes:
        """plot a histogram of all xeb errors.

        Args:
            ax: the plt.Axes to plot on. If not given, a new figure is created,
                plotted on, and shown.
            **plot_kwargs: Arguments to be passed to 'plt.Axes.plot'.

        Returns:
            The plt.Axes that was plotted on.
        """
        fig = None
        if ax is None:
            fig, ax = plt.subplots(1, 1, figsize=(8, 8))
        vis.integrated_histogram(data=self.all_errors(), ax=ax, **plot_kwargs)
        if fig is not None:
            fig.show(**plot_kwargs)
        return ax
plot a histogram of all xeb errors.

        Args:
            ax: the plt.Axes to plot on. If not given, a new figure is created,
                plotted on, and shown.
            **plot_kwargs: Arguments to be passed to 'plt.Axes.plot'.

        Returns:
            The plt.Axes that was plotted on.
        
cirq-core/cirq/experiments/two_qubit_xeb.py