code: @Override
      public INDArray eye(long n) {
          INDArray ret = Nd4j.create(n, n);
          for (int i = 0; i < n; i++) {
              ret.put(i, i, 1.0);
          }
  
          return ret.reshape(n, n);
  
      }
docs: Create the identity ndarray
  
  @param n the number for the identity
  @return