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: command_implementation.rb
    path of file: ./repos/markup/lib/github/markup
    
    the code of the file until where you have to start completion: begin
  require "posix-spawn"
rescue LoadError
  require "open3"
end

require "github/markup/implementation"


module
    
      def call_block(rendered, content)
        if block && block.arity == 2
          block.call(rendered, content)
        elsif block
          block.call(rendered)
        else
          rendered
        end