class_docstr: DAGNode class maintains useful information for a partition (submodule),
  and its input submodules and output submodules.
code: def __str__(self) -> str:
      return str(self.submodule_node)
  
imports: import operator
  from collections import deque
  from typing import Dict, List, Set, NamedTuple, Tuple, Deque
  import torch
  from torch.fx.passes.graph_manipulation import get_size_of_all_nodes
  from torch.fx.experimental.partitioner_utils import Partition, Device, PartitionerConfig, get_partition_to_latency_mapping, get_latency_of_partitioned_graph, NodeLatency, get_extra_size_of, PartitionMode
  from torch.fx.graph_module import GraphModule
  from torch.fx.node import Node, map_arg
  from torch.fx.passes.split_module import split_module
label_desc: Use image node_id 2 for calling the DAGNode obj's underlying member method code with example usage: obj.__str__() and returns: str