Converts dcm array into Matrix3
        :param dcm: 3x3 dcm array
        :returns: Matrix3

def _dcm_array_to_matrix3(self, dcm):
        """
        Converts dcm array into Matrix3
        :param dcm: 3x3 dcm array
        :returns: Matrix3
        """
        assert(dcm.shape == (3, 3))
        a = Vector3(dcm[0][0], dcm[0][1], dcm[0][2])
        b = Vector3(dcm[1][0], dcm[1][1], dcm[1][2])
        c = Vector3(dcm[2][0], dcm[2][1], dcm[2][2])
        return Matrix3(a, b, c)