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: core.rb
    path of file: ./repos/stackneveroverflow/vendor/bundle/ruby/2.3.0/gems/rake-12.0.0/lib/rake/ext
    
    the code of the file until where you have to start completion: class Module
  # Check for an existing 
    
  def rake_extension(method) # :nodoc:
    if method_defined?(method)
      $stderr.puts "WARNING: Possible conflict with Rake extension: " +
        "#{self}##{method} already exists"
    else
      yield
    end