openrtb-core/src/main/java/com/google/openrtb/json/OpenRtbJsonFactory.java
public final <EB extends ExtendableBuilder<?, EB>> OpenRtbJsonFactory register(
      OpenRtbJsonExtReader<EB> extReader, Class<EB> msgKlass) {
    extReaders.put(msgKlass.getName(), extReader);
    return this;
  }
public final <EB extends ExtendableBuilder<?, EB>> OpenRtbJsonFactory register(
      OpenRtbJsonExtReader<EB> extReader, Class<EB> msgKlass) {
    extReaders.put(msgKlass.getName(), extReader);
    return this;
  }
Register an extension reader.

@param extReader code to desserialize some extension properties
@param msgKlass class of extension message's builder, e.g. {@code MyImp.Builder.class}