code: def optimization_step():
      adam_opt.minimize(
          training_loss, var_list=model.trainable_variables
      )
  
file_path: GPflow/doc/sphinx/notebooks/tailor/gp_nn.pct.py
imports: from typing import Dict, Optional, Tuple
  import numpy
  import tensorflow
  import tensorflow_datasets
  from scipy.cluster.vq import kmeans2
  import gpflow
  from gpflow.ci_utils import reduce_in_tests
  from gpflow.utilities import to_default_float
label_desc: Use image node_id 4 for calling a global function with example usage: optimization_step() without return types