lib/promise.js
function (callback, errback) {
            if (isPromise(callback)) {
                errback = callback.errback;
                callback = callback.callback;
            }
            this.addCallback(callback);
            this.addErrback(errback);

            return this;
        }
function (callback, errback) {
            if (isPromise(callback)) {
                errback = callback.errback;
                callback = callback.callback;
            }
            this.addCallback(callback);
            this.addErrback(errback);

            return this;
        }
function ( callback , errback ) { if ( isPromise ( callback ) ) { errback = callback . errback ; callback = callback . callback ; } this . addCallback ( callback ) ; this . addErrback ( errback ) ; return this ; }
Call to specify action to take after promise completes or errors

@param {Function} [callback=null] function to call after the promise completes successfully
@param {Function} [errback=null] function to call if the promise errors

@return {comb.Promise} this promise for chaining
Call to specify action to take after promise completes or errors