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: base.rb
    path of file: ./repos/stackneveroverflow/vendor/bundle/ruby/2.3.0/gems/sass-3.4.24/lib/sass/importers
    
    the code of the file until where you have to start completion: module Sass
  module Importers
    # The abstract base class for Sass importers.
    # All importers should inherit from this.
    #
    # At the most basic level, an import
    
      def public_url(uri, sourcemap_directory)
        return if @public_url_warning_issued
        @public_url_warning_issued = true
        Sass::Util.sass_warn <<WARNING
WARNING: #{self.class.name} should define the #public_url method.
WARNING
        nil
      end