old_contents: # -*- coding: utf-8 -*-
  
  from __future__ import unicode_literals
  
  from django import dispatch
  
  
  checkout_preferences_created = dispatch.Signal(providing_args=["checkout_preferences",
                                                                 "user_checkout_identifier",
                                                                 "request"])
  """
  This signal is dispatched after the `checkout_preferences` dict is created, to
  allow the user of django-mercadopago to update the `checkout_preferences` instance:
  
  * add items and prices
  * add urls
  * validate user permissions
  * etc.
  
  To receive this signal, you can use:
  
      @receiver(checkout_preferences_created, sender=MercadoPagoService)
      def my_callback(sender, **kwargs)
          checkout_preferences = kwargs['checkout_preferences']
          user_checkout_identifier = kwargs['user_checkout_identifier']
          request = kwargs['request']
  
          (...)
  """
  
new_contents: # -*- coding: utf-8 -*-
  
  from __future__ import unicode_literals
  
  from django import dispatch
  
  
  checkout_preferences_created = dispatch.Signal(providing_args=["checkout_preferences",
                                                                 "user_checkout_identifier",
                                                                 "request"])
  
subject: Remove redundant documentation