docs: def get_instance_route53_names(self, instance):
          ''' Check if an instance is referenced in the records we have from
          Route53. If it is, return the list of domain names pointing to said
          instance. If nothing points to it, return an empty list. '''
  
          instance_attributes = [ 'public_dns_name', 'private_dns_name',
                                  'ip_address', 'private_ip_address' ]
  
          name_list = set()
  
          for attrib in instance_attributes:
              try:
                  value = getattr(instance, attrib)
              except AttributeError:
                  continue
  
              if value in self.route53_records:
                  name_list.update(self.route53_records[value])
  
          return list(name_list)