Return the fisher information matrix over the parameters
        TO CHECK: IT DOES NOT WORK PROPERLY

def getFisher(self):
        """
        Return the fisher information matrix over the parameters
        TO CHECK: IT DOES NOT WORK PROPERLY
        """
        Ctot = self.vd.getGP().getCovar()
        Ki = SP.linalg.inv(Ctot.K())
        n_scales = self.vd.getNumberScales()
        out = SP.zeros((n_scales,n_scales))
        for m in range(n_scales):
            out[m,m] = 0.5 * SP.trace(SP.dot(Ki,SP.dot(Ctot.Kgrad_param(m),SP.dot(Ki,Ctot.Kgrad_param(m)))))
            for n in range(m):
                out[m,n]=0.5 * SP.trace(SP.dot(Ki,SP.dot(Ctot.Kgrad_param(m),SP.dot(Ki,Ctot.Kgrad_param(n)))))
                out[n,m]=out[m,n]
        return out