message: [tf.contrib.slim] Update documentation in evaluation.py
diff: @@ -22,7 +22,8 @@ modules using a variety of metrics and summarizing the results.
  **********************
  In the simplest use case, we use a model to create the predictions, then specify
  -the metrics and finally call the `evaluation` method:
  +the metrics and choose one model checkpoint, finally call the`evaluation_once`
  +method:
  # Create model and obtain the predictions:
  images, labels = LoadData(...)
  @@ -34,13 +35,17 @@ the metrics and finally call the `evaluation` method:
  "mse": slim.metrics.mean_squared_error(predictions, labels),
  })
  + checkpoint_path = '/tmp/my_model_dir/my_checkpoint'
  + log_dir = '/tmp/my_model_eval/'
  +
  initial_op = tf.group(
  tf.global_variables_initializer(),
  tf.local_variables_initializer())
  - with tf.Session() as sess:
  - metric_values = slim.evaluation(
  - sess,
  + metric_values = slim.evaluate_once(
  + master='',
  + checkpoint_path=checkpoint_path,
  + log_dir=log_dir,
  num_evals=1,
  initial_op=initial_op,
  eval_op=names_to_updates.values(),
  