code: def get_apps(exclude=(), append=(), current={'apps': INSTALLED_APPS}):
      
  
      current['apps'] = tuple(
          [a for a in current['apps'] if a not in exclude]
      ) + tuple(append)
      return current['apps']
docs: Returns INSTALLED_APPS without the apps listed in exclude and with the apps
      listed in append.
  
      The use of a mutable dict is intentional, in order to preserve the state of
      the INSTALLED_APPS tuple across multiple settings files.