code: func (g *GeoM) Add(other GeoM) {
  	g.a_1 += other.a_1
  	g.b += other.b
  	g.c += other.c
  	g.d_1 += other.d_1
  	g.tx += other.tx
  	g.ty += other.ty
  }
docs: // Add is deprecated as of 1.5.0-alpha.
  // Note that this doesn't make sense as an operation for affine matrices.