import tensorflow as tf

  elif params['optimizer'] == 'adam':
    optimizer = tf.train.AdamOptimizer(learning_rate)
  elif params['optimizer'] == 'adadelta':
    optimizer = tf.train.AdadeltaOptimizer(learning_rate)
  elif params['optimizer'] == 'adagrad':
    optimizer = tf.train.AdagradOptimizer(learning_rate)
  elif params['optimizer'] == 'rmsprop':
    optimizer = tf.train.RMSPropOptimizer(
        learning_rate, momentum=params['momentum'])
  elif params['optimizer'] == 'lars':
