public UnknownFeature withImplementationDisplayName(@NotNull @Nls String implementationDisplayName) {
    return new UnknownFeature(myFeatureType, myFeatureDisplayName, myImplementationName,
                              myImplementationDisplayName == null ? implementationDisplayName : myImplementationDisplayName);
  }
public UnknownFeature withImplementationDisplayName(@NotNull @Nls String implementationDisplayName)