class_docstr: Support for `Visual Chart <www.visualchart.com>`_ binary on-disk files for
  both daily and intradaily formats.
  
  Note:
  
    - ``dataname``: Market code displayed by Visual Chart. Example: 015ES for
      EuroStoxx 50 continuous future
code: def start(self):
      super(VChartFile, self).start()
      if self._store is None:
          self._store = bt.stores.VChartFile()
          self._store.start()
  
      self._store.start(data=self)
  
      # Choose extension and extraction/calculation parameters
      if self.p.timeframe < bt.TimeFrame.Minutes:
          ext = ".tck"  # seconds will still need resampling
          # FIXME: find reference to tick counter for format
      elif self.p.timeframe < bt.TimeFrame.Days:
          ext = ".min"
          self._dtsize = 2
          self._barsize = 32
          self._barfmt = "IIffffII"
      else:
          ext = ".fd"
          self._barsize = 28
          self._dtsize = 1
          self._barfmt = "IffffII"
  
      # Construct full path
      basepath = self._store.get_datapath()
  
      # Example: 01 + 0 + 015ES + .fd -> 010015ES.fd
      dataname = "01" + "0" + self.p.dataname + ext
      # 015ES -> 0 + 015 -> 0015
      mktcode = "0" + self.p.dataname[0:3]
  
      # basepath/0015/010015ES.fd
      path = os.path.join(basepath, mktcode, dataname)
      try:
          self.f = open(path, "rb")
      except IOError:
          self.f = None
  
file_path: backtrader/backtrader/feeds/vchartfile.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  from datetime import datetime
  from struct import unpack
  import os.path
  import backtrader
  from backtrader import date2num
label_desc: Use image node_id 1 for calling the VChartFile obj's underlying member method code with example usage: obj.start() without return types