code: public static SparseTensor diagonal(int[] dimensionNumbers, int[] dimensionSizes, double value) {
      int minDimensionSize = Ints.min(dimensionSizes);
      double[] values = new double[minDimensionSize];
      Arrays.fill(values, value);
  
      return diagonal(dimensionNumbers, dimensionSizes, values);
    }
docs: Creates a tensor whose only non-zero entries are on its main
  diagonal.
  
  @param dimensionNumbers
  @param dimensionSizes
  @param value weight assigned to the keys on the main diagonal.
  @return