code: def __init__(self):
      # Inform the platform about the minimum period needs
      minbuffer = self._calcbuffer()
      self.addminperiod(minbuffer)
  
      # Structures/variable to keep synchronization
      self.pvol = dict()
      self.vcount = collections.defaultdict(int)
  
      self.days = 0
      self.dtlast = datetime.date.min
  
      # Done after calc to ensure coop inheritance and composition work
      super(RelativeVolumeByBar, self).__init__()
  
file_path: backtrader/samples/relative-volume/relvolbybar.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import collections
  import datetime
  import math
  import backtrader
label_desc: Use image node_id 2 to create a new RelativeVolumeByBar object from inherited base classes: bt with example: obj = RelativeVolumeByBar()