Gets the stability criteria from the symmetric
        Wallace tensor from an input vector and stress
        value.

        Args:
            s (float): Stress value at which to evaluate
                the stability criteria
            n (3x1 array-like): direction of the applied
                stress

def get_stability_criteria(self, s, n):
        """
        Gets the stability criteria from the symmetric
        Wallace tensor from an input vector and stress
        value.

        Args:
            s (float): Stress value at which to evaluate
                the stability criteria
            n (3x1 array-like): direction of the applied
                stress
        """
        n = get_uvec(n)
        stress = s * np.outer(n, n)
        sym_wallace = self.get_symmetric_wallace_tensor(stress)
        return np.linalg.det(sym_wallace.voigt)