def METHOD_NAME(
    self, ax: Optional[plt.Axes] = None, include_fit: bool = False, **plot_kwargs: Any
) -> plt.Axes:
    """Plots the excited state probability vs the amount of delay.
    Args:
        ax: the plt.Axes to plot on. If not given, a new figure is created,
            plotted on, and shown.
        include_fit: boolean to include exponential decay fit on graph
        **plot_kwargs: Arguments to be passed to 'plt.Axes.plot'.
    Returns:
        The plt.Axes containing the plot.
    """
    show_plot = not ax
    if show_plot:
        fig, ax = plt.subplots(1, 1, figsize=(8, 8))
    assert ax is not None
    ax.set_ylim(ymin=0, ymax=1)
    xs = self._data['delay_ns']
    ts = self._data['true_count']
    fs = self._data['false_count']
    ax.METHOD_NAME(xs, ts / (fs + ts), 'ro-', **plot_kwargs)
    if include_fit and not np.isnan(self.constant):
        ax.METHOD_NAME(xs, np.exp(-xs / self.constant), label='curve fit')
        plt.legend()
    ax.set_xlabel(r"Delay between initialization and measurement (nanoseconds)")
    ax.set_ylabel('Excited State Probability')
    ax.set_title('T1 Decay Experiment Data')
    if show_plot:
        fig.show()
    return ax