code: def darts_training(tf, session, loss, feed_dict):
      global _optimizer, _train_op
      if _optimizer is None:
          _optimizer = tf.MomentumOptimizer(learning_rate=0.025)
          # TODO: Calculate loss
          grads_and_vars = _optimizer.compute_gradients(
              loss, _arch_logits_list
          )
          _train_op = _optimizer.apply_gradients(grads_and_vars)
      session.run(_train_op)
  
file_path: nni/nni/common/nas_utils.py
imports: import functools
  import logging
  from ..None import trial
label_desc: Use image node_id 8 for calling a global function with example usage: darts_training(tf, session, loss, feed_dict) without return types