code: public static <T extends Transform> T multiply (
          double am00, double am01, double am10, double am11, double atx, double aty,
          double bm00, double bm01, double bm10, double bm11, double btx, double bty, T into) {
          into.setTransform(am00 * bm00 + am10 * bm01,
                            am01 * bm00 + am11 * bm01,
                            am00 * bm10 + am10 * bm11,
                            am01 * bm10 + am11 * bm11,
                            am00 *  btx + am10 *  bty + atx,
                            am01 *  btx + am11 *  bty + aty);
          return into;
      }
docs: Multiplies the supplied two affine transforms, storing the result in {@code into}.
  @return {@code into} for chaining.