class_docstr: Classes provides an iteration message generator function.
  The generator should yield IterationMessage instances.
class_docstr_tok: ["Classes","provides","an","iteration","message","generator","function",".","The","generator","should","yield","IterationMessage","instances","."]
code: def __init__(
      self,
      initial_iter=0,
      final_iter=0,
      validation_every_n=0,
      validation_max_iter=0,
      is_training_action=True,
      **_unused,
  ):
      self.initial_iter = max(initial_iter, -1)
      self.final_iter = max(final_iter, self.initial_iter)
      self.validation_every_n = validation_every_n
      self.validation_max_iter = validation_max_iter
      self.is_training_action = is_training_action
  
imports: import itertools
  import time
  from niftynet.engine.application_variables import CONSOLE, TF_SUMMARIES
  from niftynet.engine.signal import TRAIN, VALID, INFER
  from niftynet.utilities.util_common import look_up_operations
label_desc: Use image node_id 1 to create a new IterationMessageGenerator object from inherited base classes: object with example: obj = IterationMessageGenerator(initial_iter, final_iter, validation_every_n, validation_max_iter, is_training_action)