old_contents: # -*- coding: utf-8 -*-
  from functools import singledispatch
  
  
  @singledispatch
  def stringify(arg):
      return str(arg)
  
  
  @stringify.register(str)
  def do_not_stringify(arg):
      return arg
  
  
  @stringify.register(tuple)
  @stringify.register(list)
  @stringify.register(set)
  def stringify_list(arg):
      return ','.join([str(o) for o in arg])
  
new_contents: # -*- coding: utf-8 -*-
  from functools import singledispatch
  
  
  @singledispatch
  def stringify(arg):
      return str(arg)
  
  
  @stringify.register(str)
  def do_not_stringify(arg):
      return arg
  
  
  @stringify.register(tuple)
  @stringify.register(list)
  @stringify.register(set)
  def stringify_list(arg):
      return ','.join([str(o) for o in arg])
  
  
  @stringify.register(bool)
  def stringify_boolean(arg):
      return str(arg).lower()
  
subject: Add stringify_boolean