def set_classes(options):
 if options.has_key('class'):
  assert (not options.has_key('classes'))
  options['classes'] = options['class']
  del options['class']

def set_classes ( options ) : if options . has_key ( 'class' ) : assert ( not options . has_key ( 'classes' ) ) options [ 'classes' ] = options [ 'class' ] del options [ 'class' ]
auxiliary function to set options[classes] and delete options[class] .