code: @Override
      public Converter getConverter(Class<?> from, Class<?> to) {
          Map<Class<?>, Converter> toMap = fromMap.get(from);
          if (toMap != null) {
              return toMap.get(to);
          } else {
              return null;
          }
      }
docs: Get the desired converter.
  
  @param from
  @param to
  @return