docs: function validEvent(eventKeys, typeKeys, emitter, typeName) {
  
      if (eventKeys.length > typeKeys.length) {
        emitter.emit('error', 'An event has more properties than its type, ' + typeName +
          '. Event properties: [' + eventKeys + ']. ' + typeName + ' properties: [' + typeKeys + '].');
        return false;
      } else {
  
        for (var i = 0; i < eventKeys.length; i++) {
          if (typeKeys.indexOf(eventKeys[i]) === -1) {
            emitter.emit('error', 'An event has property "' + eventKeys[i] + '" which is not in its type, ' + typeName +
              '. Event properties: [' + eventKeys + ']. ' + typeName + ' properties: [' + typeKeys + '].');
            return false;
          }
        }
        return true;
      }
    }