code: function getHolidays(db, callback) {
  
    // Check cache for holidays
    let cacheKey = db.id + "-" + 'holidays';
    let cache = cache_holidays.get(cacheKey);
    if ( cache !== null ) {
      return callback(null, cache);
    }
  
    // Build select statement
    let select = "SELECT date, holiday_name, peak, service_info FROM rt_holidays";
  
    // Query the database
    db.select(select, function(err, results) {
  
      // Database Query Error
      if ( err ) {
        return callback(err);
      }
  
      // list of Holidays to return
      let rtn = [];
  
      // Parse each row of the results
      for ( let i = 0; i < results.length; i++ ) {
        let row = results[i];
  
        // Build holiday
        let holiday = new Holiday(
          row.date,
          row.holiday_name,
          row.peak,
          row.service_info
        );
  
        // Add holiday to list
        rtn.push(holiday);
      }
  
      // Add Holidays to cache
      cache_holidays.put(cacheKey, rtn);
  
      // Return list of holidays with callback
      return callback(null, rtn);
  
    });
  
  }
docs: ==== QUERY FUNCTIONS ==== // 
  Get a list of Holidays that are stored in the specified
  database.
  
  @param {RightTrackDB} db The Right Track DB to query
  @param {function} callback Callback function
  @param {Error} callback.error Database Query Error
  @param {Holiday[]} [callback.holidays] The selected Holidays