module ActiveSupport::Callbacks::ClassMethods

def __update_callbacks(name) # :nodoc:

:nodoc:
CallbackChain.
This is used internally to append, prepend and skip callbacks to the 
def __update_callbacks(name) # :nodoc:
  self.descendants.prepend(self).reverse_each do |target|
    chain = target.get_callbacks name
    yield target, chain.dup
  end
end