class_docstr: Represents an actor method invocation in a Ray function DAG.
code: def __str__(self) -> str:
      return get_dag_node_str(self, f"{self._method_name}()")
  
imports: from weakref import ReferenceType
  import ray
  from ray.dag.dag_node import DAGNode
  from ray.dag.input_node import InputNode
  from ray.dag.format_utils import get_dag_node_str
  from ray.dag.constants import PARENT_CLASS_NODE_KEY, PREV_CLASS_METHOD_CALL_KEY
  from ray.util.annotations import DeveloperAPI
  from typing import Any, Dict, List, Union, Tuple, Optional
label_desc: Use image node_id 4 for calling the ClassMethodNode obj's underlying member method code with example usage: obj.__str__() and returns: get_dag_node_str