PDF for Inverse Wishart prior

        Parameters
        ----------
        x : float
            Covariance matrix for which the prior is being formed over

        Returns
        ----------
        - p(x)

def pdf(self, X):
        """
        PDF for Inverse Wishart prior

        Parameters
        ----------
        x : float
            Covariance matrix for which the prior is being formed over

        Returns
        ----------
        - p(x)
        """              
        return invwishart.pdf(X, df=self.v, scale=self.Psi)