code: protected GenericConverter getDefaultConverter(TypeDescriptor sourceType, TypeDescriptor targetType) {
  		return (sourceType.isAssignableTo(targetType) ? NO_OP_CONVERTER : null);
  	}
docs: Return the default converter if no converter is found for the given sourceType/targetType pair.
  Returns a NO_OP Converter if the sourceType is assignable to the targetType.
  Returns {@code null} otherwise, indicating no suitable converter could be found.
  Subclasses may override.
  @param sourceType the source type to convert from
  @param targetType the target type to convert to
  @return the default generic converter that will perform the conversion