code: def append(self, instance):
      self.instances.append(instance)
      self.utilized_instances = self.instances
  
imports: from nvidia.dali import backend
  from nvidia.dali import tensors
  from nvidia.dali import types
  from nvidia.dali._multiproc.messages import TaskArgs, SampleRange
  import nvidia.dali.types
  from nvidia.dali._utils.external_source_impl import get_callback_from_source, accepted_arg_count, SourceKind
label_desc: Use image node_id 2 for calling the _ExternalSourceGroup obj's underlying member method code with example usage: obj.append(instance) without return types