docs: function getKeys(compositeKey) {
    if (typeof compositeKey === 'string') {
      // else assume string and split around dots
      let keyList = keyMap[compositeKey];
      if (!keyList) {
        keyList = compositeKey.split('.');
        keyMap[compositeKey] = keyList;
      }
      return keyList;
    }
    // Wrap in array if needed
    return Array.isArray(compositeKey) ? compositeKey : [compositeKey];
  }