Pair = function() {

                /**
                 * Encoder.
                 * @type {!PSON.Encoder}
                 * @expose
                 */
                this.encoder;

                /**
                 * Decoder.
                 * @type {!PSON.Decoder}
                 * @expose
                 */
                this.decoder;
            }
Constructs a new abstract PSON encoder and decoder pair.
@exports PSON.Pair
@class An abstract PSON encoder and decoder pair.
@constructor
@abstract