brew/Library/Homebrew/cask/lib/hbc/topological_hash.rb

require "tsort"

# a basic topologically sortable hashmap
module Hbc
  class TopologicalHash < Hash
    include TSort

    alias tsort_each_node each_key

    def tsort_each_child(node, &block)
      fetch(node).each(&block)
    end
  end
end