def plot_mean_and_CI(axes, mean, lb, ub, label, freqs, linestyle='-'):
    """ Plot mean and confidence boundaries.

        Args:
        axes: plt.axes
        mean: np.ndarray
        lb: np.ndarray
        ub: np.ndarray
        label: string
        freqs: list
        linestyle: string

        Returns: plt.axes

        """

    axes.fill_between(freqs, ub, lb, alpha=.25)
    axes.plot(freqs, mean, label=label, marker = 'o', linestyle=linestyle)

    return axes