anchor.diff:             ]
          )
   
  -    nodes = response['Reservations']
  +    classes = []
   
  -    classes = []
  -    for instance in nodes:
  -        classes.append(list(filter(lambda t: t['Key'] == 'aws_migration', instance['Instances'][0]['Tags']))[0]['Value'])
  +    reservations = response['Reservations']
  +    for reservation in reservations:
  +        instances = reservation['Instances']
  +        for instance in instances:
  +            classes.append(list(filter(lambda t: t['Key'] == 'aws_migration', instance['Tags']))[0]['Value'])
   
       return(sorted(set(classes)))
   
  
positive.code:                    ]
                 )
  
      nodes = response['Reservations']
  
      return [
          "%s:%s" % (
              instance['Instances'][0]['PrivateDnsName'],
              next(
                  filter(
                      lambda t: t['Key'] == 'aws_hostname',
                      instance['Instances'][0]['Tags']
                  )
              )['Value']
          )
          for instance in list(nodes)
      ]
  
  def ec2_classes(stackname):
  
negative.code:     response = client.describe_instances(InstanceIds=[instance_id])
      key = 'PrivateDnsName'
      host = response['Reservations'][0]['Instances'][0]['NetworkInterfaces'][0]
  
      if not key in host:
          print("The instance attribute {} does not exist".format(key))
          exit(1)
  