code: def ping(self):
      return "ok"
  
file_path: ray/python/ray/tests/test_memory_scheduling.py
imports: import numpy
  import time
  import ray
  from ray._private.test_utils import wait_for_condition
label_desc: Use image node_id 2 for calling the Actor obj's underlying member method code with example usage: obj.ping() and returns: str