code: function _attachExecMethod(qb) {
    /**
     * Create the exec function for a pass through to the datastax driver.
     *
     * @param `{Object} options` optional argument passed to datastax driver upon query execution
     * @param `{Function} cb` => function(err, result) {}
     * @returns {Client|exports|module.exports}
     */
    qb.exec = function (options, cb) {
  
      var _options = typeof options !== "undefined" && _.isFunction(options) ? {} : options
        , _cb;
  
      if (!_.has(_options, "prepare")) {
        _options.prepare = qb._execPrepare;
      }
  
      if (_.isFunction(options)) {
        _cb = options;
      }
      else if (_.isFunction(cb)) {
        _cb = cb;
      }
      else {
        _cb = _.noop;
      }
  
      if (cassandra !== null && cassandra.connected) {
        var cql = qb.cql();
        cassandra.execute(cql, qb.bindings(), _options, _cb);
      }
      else {
        _cb(new Error("Cassandra client is not initialized."));
      }
  
      // maintain chain
      return qb;
    };
  }
docs: hooks the 'exec' cassandra client method to our query builder object
  @param qb
  @private