Get the prior density of sediment memory

        Returns
        -------
        y : ndarray
            Array giving the density.
        x : ndarray
            Array of Memory (ratio) values over which the density was evaluated.

def prior_sediment_memory(*args, **kwargs):
        """Get the prior density of sediment memory

        Returns
        -------
        y : ndarray
            Array giving the density.
        x : ndarray
            Array of Memory (ratio) values over which the density was evaluated.
        """
        # "plot the prior for the memory (= accumulation rate varibility between neighbouring depths)"
        # PlotMemPrior @ Bacon.R ln 114 -> ln 1119 - 1141
        # w_a = mem_strength * mem_mean, w_b = mem_strength * (1 - mem_mean)
        # TODO(brews): Check that these stats are correctly translated to scipy.stats distribs.
        mem_shape = kwargs['mem_strength']  # aka. `mem_shape`
        mem_mean = kwargs['mem_mean']
        x = np.linspace(0, 1, 100)
        y = stats.beta.pdf(x, a=mem_shape * mem_mean,
                           b=mem_shape * (1 - mem_mean))
        return y, x