class ViewModel::GarbageCollection

def garbage_collect_references!(serialization)
  return unless serialization.has_key?('references')
  roots      = serialization.except('references')
  references = serialization['references']
  worklist = Set.new(collect_references(roots))
  visited  = Set.new
  while (live = worklist.first)
    worklist.delete(live)
    visited << live
    collect_references(references[live]) do |ref|
      worklist << ref unless visited.include?(ref)
    end
  end
  references.keep_if { |ref, _val| visited.include?(ref) }
end