class_docstr: A hook class reporting the progress of iteration.
  
  This is a hook class designed for
  :func:`~chainercv.utils.apply_prediction_to_iterator`.
  
  Args:
      n_total (int): The number of images. This argument is optional.
code: def __init__(self, n_total=None):
      self.n_total = n_total
      self.start = time.time()
      self.n_processed = 0
  
imports: from __future__ import division
  import sys
  import time
label_desc: Use image node_id 1 to create a new ProgressHook object from inherited base classes: object with example: obj = ProgressHook(n_total)