code: def optimisation_step():
      natgrad_opt.minimize(loss_fn, variational_vars)
      adam_opt.minimize(loss_fn, adam_vars)
  
imports: import matplotlib.pyplot
  import numpy
  import tensorflow
  import tensorflow_probability
  import gpflow
label_desc: Use image node_id 2 for calling a global function with example usage: optimisation_step() without return types