whole_func_string: function registerRunner(runner_id, active_at, callback) {
          if (typeof (active_at) === 'function') {
              callback = active_at;
              active_at = new Date();
          }
          if (typeof (active_at) === 'string') {
              active_at = new Date(active_at);
          }
          runners[runner_id] = {
              runner_id: runner_id,
              active_at: active_at,
              idle: false
          };
          return callback(null);
      }
func_code_string: function registerRunner(runner_id, active_at, callback) {
          if (typeof (active_at) === 'function') {
              callback = active_at;
              active_at = new Date();
          }
          if (typeof (active_at) === 'string') {
              active_at = new Date(active_at);
          }
          runners[runner_id] = {
              runner_id: runner_id,
              active_at: active_at,
              idle: false
          };
          return callback(null);
      }
func_documentation_string: Register a runner on the backend and report it's active: - runner_id - String, unique identifier for runner. - active_at - ISO String timestamp. Optional. If none is given, current time - callback - f(err)