# File lib/sugar-high/file.rb, line 167
     def self.mutate_file file, marker, place, &block
       raise ArgumentError, "You must define a replacement marker for a :before or :after key" if !marker 
              
       replace_in_file file, /(#{marker})/mi do |match|
         place == :after ? "#{match}\n  #{yield}" : "#{yield}\n  #{match}"         
       end
     end