code: def do_format(value, *args, **kwargs):
      
      if args and kwargs:
          raise FilterArgumentError('can\'t handle positional and keyword '
                                    'arguments at the same time')
      return soft_unicode(value) % (kwargs or args)
docs: Apply python string formatting on an object:
  
      .. sourcecode:: jinja
  
          {{ "%s - %s"|format("Hello?", "Foo!") }}
              -> Hello? - Foo!