Could someone please explain me what is the purpose of the following fields in the RpcMap class (they are not used)? And what is the deal with the RpcMap_CustomFieldSerializer class? I couldn't find any reference to this class.

  private Byte _byte;
  private Short _short;
  private Integer _integer;
  private Long _long;
  private Float _float;
  private Double _double;
  private Date _date;
  private Boolean _boolean;

  private Byte[] _bytes;
  private Short[] _shorts;
  private Integer[] _integers;
  private Long[] _longs;
  private Float[] _floats;
  private Double[] _doubles;
  private Date[] _dates;
  private Boolean[] _booleans;

  private List<String> _list;
  private Set<String> _set;
  private Map<String, String> _map;
Please note that I read the javadoc comment attached to RpcMap but I could not make much sense out of it.

For instance:

 * The GWT RPC rebinder generates field serializers for every type that is
 * assignable to any type in the RPC interfaces.
Where is this stuff specified? Is this referring to the BeanModelGenerator?

 * Therefore BaseModel uses "Map&lt;String, RpcField&gt; map" and relies on type
 * erasure (cast to Map&lt;Object,Object&gt;) to work around this.
There is no RpcField class, at least not in GXT 2.1.0.