code: def testGetKeys(self):
      def CacheFn(obj, arg):
          del obj
          return arg + "extra"
  
      cache = xla_client.weakref_lru_cache(lambda: None, CacheFn, 4)
  
      class WRKey:
          pass
  
      wrkey = WRKey()
  
      self.assertEmpty(cache.cache_keys())
      cache(wrkey, "arg1")
      cache(wrkey, "arg2")
      self.assertLen(cache.cache_keys(), 2)
  
file_path: tensorflow/third_party/xla/xla/python/weakref_lru_cache_test.py
imports: import threading
  import time
  from absl.testing import absltest
  from xla.python import xla_client
label_desc: Use image node_id 3 for calling the WeakrefLRUCacheTest obj's underlying member method code with example usage: obj.testGetKeys() and returns: unknown