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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _read_checkpoint_vars(model_path):
 """ return a set of strings """

        reader = tf.train.NewCheckpointReader(model_path)
        reader = CheckpointReaderAdapter(reader)    # use an adapter to standardize the name
        ckpt_vars = reader.get_variable_to_shape_map().keys()
        return reader, set(ckpt_vars)