code: def _prefix_to_checkpoint_path(prefix, format_version):
      """Returns the pathname of a checkpoint file, given the checkpoint prefix.
  
      For V1 checkpoint, simply returns the prefix itself (the data file).  For V2,
      returns the pathname to the index file.
  
      Args:
        prefix: a string, the prefix of a checkpoint.
        format_version: the checkpoint format version that corresponds to the
          prefix.
      Returns:
        The pathname of a checkpoint file, taking into account the checkpoint
          format version.
      """
      if format_version == saver_pb2.SaverDef.V2:
          return (
              prefix + ".index"
          )  # The index file identifies a checkpoint.
      return prefix
  
imports: import collections
  import copy
  import os.path
  import re
  import time
  from google.protobuf import text_format
  from tensorflow.core.protobuf import saver_pb2
  from tensorflow.python.checkpoint import checkpoint_options
  from tensorflow.python.eager import context
  from tensorflow.python.framework import errors
  from tensorflow.python.framework import ops
  from tensorflow.python.lib.io import file_io
  from tensorflow.python.ops import variable_scope
  from tensorflow.python.platform import tf_logging
  from tensorflow.python.training import training_util
  from tensorflow.python.training.checkpoint_state_pb2 import CheckpointState
  from tensorflow.python.util import compat
  from tensorflow.python.util import deprecation
  from tensorflow.python.util.tf_export import tf_export
label_desc: Use image node_id 7 for calling a global function with example usage: _prefix_to_checkpoint_path(prefix, format_version) and returns: prefix, unknown