code: def initialize_tpu_system(cluster_resolver=None):
      """Initialize the TPU devices.
  
      Args:
        cluster_resolver: A tf.distribute.cluster_resolver.TPUClusterResolver,
            which provides information about the TPU cluster.
      Returns:
        The tf.tpu.Topology object for the topology of the TPU cluster. If called
        inside tf.function, it returns the serialized topology object instead.
  
      Raises:
        RuntimeError: If running inside a tf.function.
        NotFoundError: If no TPU devices found in eager mode.
      """
      return tpu_strategy_util.initialize_tpu_system_impl(
          cluster_resolver, TPUClusterResolver
      )
  
imports: import collections
  import re
  from tensorflow.core.protobuf.tpu import topology_pb2
  from tensorflow.python.distribute.cluster_resolver import cluster_resolver
  from tensorflow.python.eager import remote
  from tensorflow.python.framework import config
  from tensorflow.python.framework import errors
  from tensorflow.python.platform import tf_logging
  from tensorflow.python.tpu import tpu_strategy_util
  from tensorflow.python.tpu import tpu_system_metadata
  from tensorflow.python.training import server_lib
  from tensorflow.python.util import compat
label_desc: Use image node_id 2 for calling a global function with example usage: initialize_tpu_system(cluster_resolver) and returns: tpu_strategy_util