class_docstr: Broker implementation for VisualChart.
  
  This class maps the orders/positions from VisualChart to the
  internal API of ``backtrader``.
  
  Params:
  
    - ``account`` (default: None)
  
      VisualChart supports several accounts simultaneously on the broker. If
      the default ``None`` is in place the 1st account in the ComTrader
      ``Accounts`` collection will be used.
  
      If an account name is provided, the ``Accounts`` collection will be
      checked and used if present
  
    - ``commission`` (default: None)
  
      An object will be autogenerated if no commission-scheme is passed as
      parameter
  
      See the notes below for further explanations
  
  Notes:
  
    - Position
  
      VisualChart reports "OpenPositions" updates through the ComTrader
      interface but only when the position has a "size". An update to
      indicate a position has moved to ZERO is reported by the absence of
      such position. This forces to keep accounting of the positions by
      looking at the execution events, just like the simulation broker does
  
    - Commission
  
      The ComTrader interface of VisualChart does not report commissions and
      as such the auto-generated CommissionInfo object cannot use
      non-existent commissions to properly account for them. In order to
      support commissions a ``commission`` parameter has to be passed with
      the appropriate commission schemes.
  
      The documentation on Commission Schemes details how to do this
  
    - Expiration Timing
  
      The ComTrader interface (or is it the comtypes module?) discards
      ``time`` information from ``datetime`` objects and expiration dates are
      always full dates.
  
    - Expiration Reporting
  
      At the moment no heuristic is in place to determine when a cancelled
      order has been cancelled due to expiration. And therefore expired
      orders are reported as cancelled.
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code: def OnModifiedOrder(self, Order):
      # We are not expecting this: unless backtrader starts implementing
      # modify order method
      pass
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import collections
  from datetime import date, datetime, timedelta
  import threading
  from backtrader import BrokerBase, Order, BuyOrder, SellOrder
  from backtrader.comminfo import CommInfoBase
  from backtrader.feed import DataBase
  from backtrader.metabase import MetaParams
  from backtrader.position import Position
  from backtrader.utils.py3 import with_metaclass
  from backtrader.stores import vcstore
label_desc: Use image node_id 17 for calling the VCBroker obj's underlying member method code with example usage: obj.OnModifiedOrder(Order) without return types