Returns the angles (alpha, beta, gamma) of the lattice.

def angles(self) -> Tuple[float]:
        """
        Returns the angles (alpha, beta, gamma) of the lattice.
        """
        m = self._matrix
        lengths = self.lengths
        angles = np.zeros(3)
        for i in range(3):
            j = (i + 1) % 3
            k = (i + 2) % 3
            angles[i] = abs_cap(dot(m[j], m[k]) / (lengths[j] * lengths[k]))
        angles = np.arccos(angles) * 180.0 / pi
        return tuple(angles.tolist())