updateUtterancesList = function (srcCollection, tgtCollection, attribute) {
    (srcCollection || []).forEach(srcItem => {
        let matchInTarget = tgtCollection.find(item => item.intent.name == srcItem.intent);
        if(!matchInTarget || matchInTarget.utterances.length === 0) {
            addUtteranceToCollection(attribute, srcItem, matchInTarget);
            return;
        }
        if(!matchInTarget.utterances.find(item => item.text == srcItem[attribute])) {
            addUtteranceToCollection(attribute, srcItem, matchInTarget);
            return;
        }
    });
}
helper function to add utterances to collection if it does not exist
@param {object[]} tgtCollection target collection of utterance objects
@param {object []} srcCollection source collection of utterance objects
@param {string} attribute attribute to check on and copy over
@returns {void}