How to convert mutliple Matrix in Eigen to json with Jsoncpp?

Question

I need to save my data in Eigen. I have some Matrix and other information that need to be save into json.

But I cannot find any useful document. Do you have any advise?

\\ here is my data, a simple example
#include <Eigen/Core>
#include <json/json.h>
....
....

void main(int argc, char *argv[]){
    int Type;
    MatrixXf m1;
    MatrixXf m2;

    // init data, this is not important
    m1 << 1, 2, 3,
         4, 5, 6,
         7, 8, 9;
    m2 << 1, 2, 3,
         4, 5, 6,
         7, 8, 9;

    // how to save to json file?
    // {
    //  "Type":0,
    //  "m1":[[1,2,3],[4,5,6],[7,8,9]],
    //   "m2":[[1,2,3],[4,5,6],[7,8,9]],
    // }

}