    void Tool::addFieldOptions() {
        add_options()
        ("fields,f" , po::value<string>() , "comma separated list of field names e.g. -f name,age" )
        ("fieldFile" , po::value<string>() , "file with fields names - 1 per line" )
        ;
    }
    void Tool::addFieldOptions() {
        add_options()
        ("fields,f" , po::value<string>() , "comma separated list of field names e.g. -f name,age" )
        ("fieldFile" , po::value<string>() , "file with fields names - 1 per line" )
        ;
    }