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: observer.rb
    path of file: ./repos/opal/stdlib
    
    the code of the file until where you have to start completion: #
# Implementation of the _Observer_ object-oriented design pattern.  The
# following documentation is copied, with
    
  def notify_observers(*arg)
    if defined? @observer_state and @observer_state
      if defined? @observer_peers
        @observer_peers.each do |k, v|
          k.send v, *arg
        end
      end