code: public void encodeValue(Writer writer, T obj) throws IOException {
  		int count = 0;
  		for (String key : map.keySet()) {
  			JsonUtil.putKey(writer, key);
  			JsonPropertyCoder<T, ?> enc = map.get(key);
  			enc.encode(writer, obj);
  			count++;
  			if (count != map.size()) {
  				JsonUtil.addSeparator(writer);
  			}
  		}
  	}
docs: *** Internal use only; please do not call directly. ***<br>
  *** Public access granted only to allow reusing from other packages. ***
  
  @param writer {@link Writer}
  @param obj value
  @throws IOException
  @author vvakame