code: def start(self):
      self.callcounter = 0
      txtfields = list()
      txtfields.append("Len")
      txtfields.append("Datetime")
      txtfields.append("Open")
      txtfields.append("High")
      txtfields.append("Low")
      txtfields.append("Close")
      txtfields.append("Volume")
      txtfields.append("OpenInterest")
      print(",".join(txtfields))
  
      self.doop = 0
  
file_path: backtrader/samples/volumefilling/volumefilling.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import argparse
  import datetime
  import os.path
  import time
  import sys
  import backtrader
label_desc: Use image node_id 3 for calling the St obj's underlying member method code with example usage: obj.start() without return types