anchor.diff:  def main():
       opts, args = parser.parse_args()
   
  -    if opts.node_class:
  +    if opts.classes:
  +        classes = ec2_classes(stackname)
  +        print("\n".join(classes))
  +        exit(0)
  +
  +    elif opts.node_class:
           if any('-' in c for c in opts.node_class):
               parser.error('Node classes should not use hyphens. Hint: Try an underscore')
   
  
positive.code: 
      return(hosts)
  
  def get_hostname_by_id(instance_id):
      client = boto3.client('ec2', region_name=region)
      response = client.describe_instances(InstanceIds=[instance_id])
  
negative.code:     dest='single_node',
  )
  
  parser.add_option(
      '--classes',
      help='List the available classes',
      action='store_true',
      dest='classes',
  )
  
  if __name__ == '__main__':
      main()
  
  