How to print vertical bar when using cv::CommandLineParser keys?

Solution for How to print vertical bar when using cv::CommandLineParser keys?
is Given Below:

From cv::CommandLineParser documentation:

The keys parameter is a string containing several blocks, each one is enclosed in curly braces and describes one argument. Each argument contains three parts separated by the | symbol

I would like to print vertical bar character (|) for helpful messages, specifically for bash pipe suggestions.
The following example should explain the purpose better.

#include <iostream>
#include <string>

#include <opencv2/core.hpp>

int main(int argc, char** argv) {
    const std::string keys =
        "{help h usage ? | | print this messagen"
        "tt./program $(gz topic -l | grep image) }"
        "{@image_topic | <none> | Gazebo image topic namen"
        "ttexample: /gazebo/default/typhoon_h480/cgo3_camera_link/camera/image }";
    cv::CommandLineParser parser(argc, argv, keys);
    parser.about("program");
    if (parser.has("help"))
        parser.printMessage();
    const std::string image_topic = parser.get<std::string>("@image_topic");
    std::cout << image_topic << std::endl;
    return 0;
}

./program.out –help $(gz topic -l | grep image)

program
Usage: test.out [params] image_topic 

    -?, -h, --help, --usage (value:true)
        print this message
        ./program $(gz topic -l

    image_topic (value:/gazebo/default/typhoon_h480/cgo3_camera_link/camera/image)
        Gazebo image topic name
        example: /gazebo/default/typhoon_h480/cgo3_camera_link/camera/image
/gazebo/default/typhoon_h480/cgo3_camera_link/camera/image

Help prints an undesired message.
./program $(gz topic -l

Is it possible to print vertical bar (|) when calling parser.printMessage()?