code: def train_input_fn():
      """Train input function."""
      classes = tf.constant("first", shape=[1])
      scores = tf.constant(1.0, shape=[1])
      return {
          "classes": classes,
          "scores": scores,
      }, classes
  
file_path: model-analysis/tensorflow_model_analysis/eval_saved_model/example_trainers/batch_size_limited_classifier.py
imports: import tensorflow
  from tensorflow import estimator
  from tensorflow_model_analysis.eval_saved_model import export
  from tensorflow_model_analysis.eval_saved_model.example_trainers import util
  from tensorflow.python.estimator.canned import metric_keys
  from tensorflow.python.estimator.canned import prediction_keys
label_desc: Use image node_id 2 for calling a global function with example usage: train_input_fn() and returns: dict,  classes