code: function get(callback) {
    if (file === undefined) {
      callback(
        new Error(
          os.platform() +
            ' is not supported yet, please open an issue (https://github.com/simonepri/pidtree)'
        )
      );
    }
  
    var list = require('./' + file);
    list(callback);
  }
docs: Gets the list of all the pids of the system.
  @param  {Function} callback Called when the list is ready.