docs: public static DMatrix3x3 transpose( DMatrix3x3 input , DMatrix3x3 output ) {
          if( input == null )
              input = new DMatrix3x3();
  
          output.a11 = input.a11;
          output.a12 = input.a21;
          output.a13 = input.a31;
          output.a21 = input.a12;
          output.a22 = input.a22;
          output.a23 = input.a32;
          output.a31 = input.a13;
          output.a32 = input.a23;
          output.a33 = input.a33;
  
          return output;
      }