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: heading.rb
    path of file: ./repos/stackneveroverflow/vendor/bundle/ruby/2.3.0/gems/rdoc-4.3.0/lib/rdoc/markup
    
    the code of the file until where you have to start completion: ##
# A heading with a level (1-6) and text

RDoc::M
    
  def self.to_html
    return @to_html if @to_html

    markup = RDoc::Markup.new
    markup.add_special RDoc::CrossReference::CROSSREF_REGEXP, :CROSSREF

    @to_html = RDoc::Markup::ToHtml.new nil

    def @to_html.handle_special_CROSSREF special
      special.text.sub(/^\\/, '')
    end

    @to_html
  end