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: ruby_requirement_setter.rb
    path of file: ./repos/dependabot-core/bundler/lib/dependabot/bundler/file_updater
    
    the code of the file until where you have to start completion: # typed: true
# frozen_string_literal: true

require "parser/current"
require "dependabot/bundler/file_updater"
require "dependabot/bundler/requirement"

module Dep
    
        def rewrite(content)
          return content unless gemspec_declares_ruby_requirement?

          buffer = Parser::Source::Buffer.new("(gemfile_content)")
          buffer.source = content
          ast = Parser::CurrentRuby.new.parse(buffer)

          if declares_ruby_version?(ast)
            GemfileRewriter.new(
              ruby_version: ruby_version
            ).rewrite(buffer, ast)
          else
            "ruby '#{ruby_version}'\n" + content
          end