code: def get_callback_function(setting_name, default=None):
  	
  	func = getattr(settings, setting_name, None)
  	if not func:
  		return default
  
  	if callable(func):
  		return func
  
  	if isinstance(func, str):
  		func = import_string(func)
  
  	if not callable(func):
  		raise ImproperlyConfigured("{name} must be callable.".format(name=setting_name))
  
  	return func
docs: Resolve a callback function based on a setting name.
  
  	If the setting value isn't set, default is returned.  If the setting value
  	is already a callable function, that value is used - If the setting value
  	is a string, an attempt is made to import it.  Anything else will result in
  	a failed import causing ImportError to be raised.
  
  	:param setting_name: The name of the setting to resolve a callback from.
  	:type setting_name: string (``str``/``unicode``)
  	:param default: The default to return if setting isn't populated.
  	:type default: ``bool``
  	:returns: The resolved callback function (if any).
  	:type: ``callable``