You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: observable_hash.rb
    path of file: ./repos/glimmer/lib/glimmer/data_binding
    
    the code of the file until where you have to start completion: # Copyright (c) 2007-2024 Andy Maleh
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this soft
    
      def transform_values!(&block)
        if block_given?
          old_hash = self.dup
          super(&block).tap do |new_hash|
            new_hash.keys.each do |changed_key|
              old_value = old_hash[changed_key]
              if new_hash[changed_key] != old_value
                unregister_dependent_observers(changed_key, old_value)
                unregister_dependent_observers(nil, old_value)
                notify_observers(changed_key)
              end
            end
          end