code: private static <T extends Encoder> T map(String name, T encoder) {
          Encoder old = ENCODERS_MAP.put(name, encoder);
          assert old == null;
          return encoder;
      }
docs: Internal method to setup and map encoder singletons.
  
  @param name -- name of the encoder (one of the constants above)
  @param encoder -- the encoder singleton instance
  @param <T> the encoder type
  @return the encoder argument.