protected sealed override void StoreTagSource(ITextView textViewOpt, ITextBuffer subjectBuffer, ProducerPopulatedTagSource <TTag> tagSource)
 {
     subjectBuffer.Properties.AddProperty(UniqueKey, tagSource);
 }
 internal sealed override bool TryRetrieveTagSource(ITextView textViewOpt, ITextBuffer subjectBuffer, out ProducerPopulatedTagSource <TTag> tagSource)
 {
     return(subjectBuffer.Properties.TryGetProperty(UniqueKey, out tagSource));
 }