int cvGraphAddVtx(CvGraph* graph, CvGraphVtx* vtx, CvGraphVtx** inserted_vtx) {
    void *fptr;
    int retval;

    fptr = dlsym(_Chcv_handle, "cvGraphAddVtx_chdl");
    if(fptr == NULL) {
        fprintf(_stderr, "Error: %s(): dlsym(): %s\n", __func__,  dlerror());
        return -1;
    }
    dlrunfun(fptr, &retval, cvGraphAddVtx, graph, vtx, inserted_vtx);
    return retval;
}
