Softplus

     Operand<TFloat32> input = tf.constant(
              new float[] {-20f, -1.0f, 0.0f, 1.0f, 20f});
     Softplus<TFloat32> softplus = new Softplus<>(tf);
     Operand<TFloat32> result = softplus.call(input);
     // result is [2.0611537e-09f, 3.1326166e-01f, 6.9314718e-01f,
     //                 1.3132616e+00f, 2.0000000e+01f]