code: public static VTensor combine(VTensor t1, VTensor t2) {
          checkSameDims(t1, t2);
          checkSameAlgebra(t1, t2);
          
          int[] dims3 = IntArrays.insertEntry(t1.getDims(), 0, 2);
          VTensor y = new VTensor(t1.s, dims3);
          y.addTensor(t1, 0, 0);
          y.addTensor(t2, 0, 1);
          return y;
      }
docs: Combines two identically sized tensors by adding an initial dimension of size 2.
  @param t1 The first tensor to add.
  @param t2 The second tensor to add.
  @return The combined tensor.