ConcatRegexFeatures is giving warning as same name is
used for different feature ids which is an indicator of
some problem in feature id generation.
Here is how to reproduce it.
addFeature(new FeatureTypesEachLabel(this, new
ConcatRegexFeatures(this, -1, 1))))
Basically set the relSegmentStart and relSegmentEnd to
(-1, 1) and run iitb.Segment.Segment package.
Looks like idBase variable is set to 2^(window-1)
instead of 2^window in ConcatRegexFeatures.