class RuboCop::Cop::Style::ModuleFunction

def on_module(node)
  return unless node.body&.begin_type?
  each_wrong_style(node.body.children) do |child_node|
    add_offense(child_node) do |corrector|
      next if style == :forbidden
      if extend_self_node?(child_node)
        corrector.replace(child_node, 'module_function')
      else
        corrector.replace(child_node, 'extend self')
      end
    end
  end
end