code: def log(self, txt, dt=None, nodate=False):
      if not nodate:
          dt = dt or self.data.datetime[0]
          dt = bt.num2date(dt)
          print("%s, %s" % (dt.isoformat(), txt))
      else:
          print("---------- %s" % (txt))
  
file_path: backtrader/tests/test_strategy_unoptimized.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import time
  import testcommon
  import backtrader
  import backtrader.indicators
label_desc: Use image node_id 1 for calling the TestStrategy obj's underlying member method code with example usage: obj.log(txt, dt, nodate) without return types