code: def __init__(self, model, Xtest, Ytest, holdout_interval=10):
      self.model = model
      self.holdout_interval = holdout_interval
      self.Xtest = Xtest
      self.Ytest = Ytest
      self.log_likelihoods = []
      self.hold_out_likelihood = []
      self.n_iters = []
      self.counter = 0
  
file_path: GPflow/doc/sphinx/notebooks/theory/FITCvsVFE.py
imports: import numpy
  import tensorflow
  import gpflow
  from gpflow.ci_utils import reduce_in_tests
label_desc: Use image node_id 1 to create a new Callback object  with example: obj = Callback(model, Xtest, Ytest, holdout_interval)