code: def __init__(self, volmax):
      self.volmax = volmax
      magnitude = 0
      self.divisor = 1.0
      while abs(volmax / self.divisor) >= 1000:
          magnitude += 1
          self.divisor *= 1000.0
  
      self.suffix = self.Suffixes[magnitude]
  
file_path: backtrader/backtrader/plot/formatters.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import matplotlib.dates
  import matplotlib.ticker
  from ..utils import num2date
label_desc: Use image node_id 1 to create a new MyVolFormatter object from inherited base classes: mplticker with example: obj = MyVolFormatter(volmax)