code: def start(self):
      if self.p.outfile is None:
          self.f = sys.stdout
      else:
          self.f = open(self.p.outfile, "wb")
  
      if self.data._timeframe < bt.TimeFrame.Days:
          headers = "Date,Time,Open,High,Low,Close,Volume,OpenInterest"
      else:
          headers = "Date,Open,High,Low,Close,Volume,OpenInterest"
  
      headers += "\n"
      self.f.write(bytes(headers))
  
file_path: backtrader/tools/rewrite-data.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
  from backtrader.utils.py3 import bytes
label_desc: Use image node_id 1 for calling the RewriteStrategy obj's underlying member method code with example usage: obj.start() without return types