/usr/lib/ruby/ is in ruby-graphviz 1.2.3-1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/ext/
/usr/lib/ruby/vendor_ruby/ext/gvpr/
/usr/lib/ruby/vendor_ruby/ext/gvpr/dot2ruby.g
/usr/lib/ruby/vendor_ruby/graphviz/
/usr/lib/ruby/vendor_ruby/graphviz/attrs.rb
/usr/lib/ruby/vendor_ruby/graphviz/constants.rb
/usr/lib/ruby/vendor_ruby/graphviz/core_ext.rb
/usr/lib/ruby/vendor_ruby/graphviz/dot2ruby.rb
/usr/lib/ruby/vendor_ruby/graphviz/dot_script.rb
/usr/lib/ruby/vendor_ruby/graphviz/dsl.rb
/usr/lib/ruby/vendor_ruby/graphviz/edge.rb
/usr/lib/ruby/vendor_ruby/graphviz/elements.rb
/usr/lib/ruby/vendor_ruby/graphviz/ext.rb
/usr/lib/ruby/vendor_ruby/graphviz/family_tree/
/usr/lib/ruby/vendor_ruby/graphviz/family_tree/couple.rb
/usr/lib/ruby/vendor_ruby/graphviz/family_tree/generation.rb
/usr/lib/ruby/vendor_ruby/graphviz/family_tree/person.rb
/usr/lib/ruby/vendor_ruby/graphviz/family_tree/sibling.rb
/usr/lib/ruby/vendor_ruby/graphviz/family_tree.rb
/usr/lib/ruby/vendor_ruby/graphviz/graphml.rb
/usr/lib/ruby/vendor_ruby/graphviz/math/
/usr/lib/ruby/vendor_ruby/graphviz/math/matrix.rb
/usr/lib/ruby/vendor_ruby/graphviz/node.rb
/usr/lib/ruby/vendor_ruby/graphviz/nothugly/
/usr/lib/ruby/vendor_ruby/graphviz/nothugly/nothugly.xsl
/usr/lib/ruby/vendor_ruby/graphviz/nothugly.rb
/usr/lib/ruby/vendor_ruby/graphviz/theory.rb
/usr/lib/ruby/vendor_ruby/graphviz/types/
/usr/lib/ruby/vendor_ruby/graphviz/types/arrow_type.rb
/usr/lib/ruby/vendor_ruby/graphviz/types/color.rb
/usr/lib/ruby/vendor_ruby/graphviz/types/color_list.rb
/usr/lib/ruby/vendor_ruby/graphviz/types/esc_string.rb
/usr/lib/ruby/vendor_ruby/graphviz/types/gv_bool.rb
/usr/lib/ruby/vendor_ruby/graphviz/types/gv_double.rb
/usr/lib/ruby/vendor_ruby/graphviz/types/html_string.rb
/usr/lib/ruby/vendor_ruby/graphviz/types/lbl_string.rb
/usr/lib/ruby/vendor_ruby/graphviz/types/rect.rb
/usr/lib/ruby/vendor_ruby/graphviz/types/spline_type.rb
/usr/lib/ruby/vendor_ruby/graphviz/types.rb
/usr/lib/ruby/vendor_ruby/graphviz/utils/
/usr/lib/ruby/vendor_ruby/graphviz/utils/colors.rb
/usr/lib/ruby/vendor_ruby/graphviz/utils.rb
/usr/lib/ruby/vendor_ruby/graphviz/xml.rb
/usr/lib/ruby/vendor_ruby/graphviz.rb
/usr/lib/ruby/vendor_ruby/ruby-graphviz.rb