handleAtForPattern = function(utterance, entitiesFound, flatEntityAndRoles) {
    if (utterance.match(/{@/g)) {
        utterance = utterance.replace(/{@/g, '{');
        entitiesFound.forEach(entity => {
            if (entity.entity.match(/^@/g)) {
                entity = handleAtPrefix(entity, flatEntityAndRoles);
                if (entity.entity && entity.role) {
                    utterance = utterance.replace(`{${entity.role}}`, `{${entity.entity}:${entity.role}}`);
                }
            }
        });
    }
    return utterance;
}
Helper function to handle @ reference in patterns
@param {String} utterance 
@param {String []} entitiesFound 
@param {Object []} flatEntityAndRoles