code: func (a Affine) Mul(b Affine) Affine {
  	return Affine{
  		a[0]*b[0] + a[1]*b[3] + a[2]*b[6],
  		a[0]*b[1] + a[1]*b[4] + a[2]*b[7],
  		a[0]*b[2] + a[1]*b[5] + a[2]*b[8],
  		a[3]*b[0] + a[4]*b[3] + a[5]*b[6],
  		a[3]*b[1] + a[4]*b[4] + a[5]*b[7],
  		a[3]*b[2] + a[4]*b[5] + a[5]*b[8],
  		a[6]*b[0] + a[7]*b[3] + a[8]*b[6],
  		a[6]*b[1] + a[7]*b[4] + a[8]*b[7],
  		a[6]*b[2] + a[7]*b[5] + a[8]*b[8],
  	}
  }
docs: // Mul returns the multiplication of two affine transform matrices.