/usr/lib/ruby/ is in ruby-classifier 1.3.3-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/classifier.rb
/usr/lib/ruby/vendor_ruby/classifier/
/usr/lib/ruby/vendor_ruby/classifier/bayes.rb
/usr/lib/ruby/vendor_ruby/classifier/lsi/
/usr/lib/ruby/vendor_ruby/classifier/lsi/content_node.rb
/usr/lib/ruby/vendor_ruby/classifier/lsi/summary.rb
/usr/lib/ruby/vendor_ruby/classifier/lsi/word_list.rb
/usr/lib/ruby/vendor_ruby/classifier/extensions/
/usr/lib/ruby/vendor_ruby/classifier/extensions/word_hash.rb
/usr/lib/ruby/vendor_ruby/classifier/extensions/vector_serialize.rb
/usr/lib/ruby/vendor_ruby/classifier/extensions/vector.rb
/usr/lib/ruby/vendor_ruby/classifier/extensions/string.rb
/usr/lib/ruby/vendor_ruby/classifier/lsi.rb