isIdentity method

Implementation

bool isIdentity() =>
    _m3storage[0] == 1.0 // col 1
    &&
    _m3storage[1] == 0.0 &&
    _m3storage[2] == 0.0 &&
    _m3storage[3] == 0.0 // col 2
    &&
    _m3storage[4] == 1.0 &&
    _m3storage[5] == 0.0 &&
    _m3storage[6] == 0.0 // col 3
    &&
    _m3storage[7] == 0.0 &&
    _m3storage[8] == 1.0;