/usr/lib/ruby/ is in ruby-contracts 0.16.0-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/contracts/
/usr/lib/ruby/vendor_ruby/contracts/attrs.rb
/usr/lib/ruby/vendor_ruby/contracts/builtin_contracts.rb
/usr/lib/ruby/vendor_ruby/contracts/call_with.rb
/usr/lib/ruby/vendor_ruby/contracts/core.rb
/usr/lib/ruby/vendor_ruby/contracts/decorators.rb
/usr/lib/ruby/vendor_ruby/contracts/engine/
/usr/lib/ruby/vendor_ruby/contracts/engine/base.rb
/usr/lib/ruby/vendor_ruby/contracts/engine/eigenclass.rb
/usr/lib/ruby/vendor_ruby/contracts/engine/target.rb
/usr/lib/ruby/vendor_ruby/contracts/engine.rb
/usr/lib/ruby/vendor_ruby/contracts/errors.rb
/usr/lib/ruby/vendor_ruby/contracts/formatters.rb
/usr/lib/ruby/vendor_ruby/contracts/invariants.rb
/usr/lib/ruby/vendor_ruby/contracts/method_handler.rb
/usr/lib/ruby/vendor_ruby/contracts/method_reference.rb
/usr/lib/ruby/vendor_ruby/contracts/support.rb
/usr/lib/ruby/vendor_ruby/contracts/validators.rb
/usr/lib/ruby/vendor_ruby/contracts/version.rb
/usr/lib/ruby/vendor_ruby/contracts.rb