def METHOD_NAME(self, ax=None, **kwargs):
    """Plot correlation matrix.
    Parameters
    ----------
    ax : `~matplotlib.axes.Axes`, optional
        Axis to plot on.
    **kwargs : dict
        Keyword arguments passed to `~gammapy.visualization.plot_heatmap`
    Returns
    -------
    ax : `~matplotlib.axes.Axes`, optional
        Axis
    """
    from gammapy.visualization import annotate_heatmap, plot_heatmap
    npars = len(self.parameters)
    figsize = (npars * 0.8, npars * 0.65)
    plt.figure(figsize=figsize)
    ax = plt.gca() if ax is None else ax
    kwargs.setdefault("cmap", "coolwarm")
    names = self.parameters.names
    im, cbar = plot_heatmap(
        data=self.correlation,
        col_labels=names,
        row_labels=names,
        ax=ax,
        vmin=-1,
        vmax=1,
        cbarlabel="Correlation",
        **kwargs,
    )
    annotate_heatmap(im=im)
    return ax