class_docstr: A marker for subdividing the period at the latest intraperiod capital
  change. prev_subperiod and curr_subperiod hold information respective to
  the previous and current subperiods.
code: def __init__(
      self,
      prev_returns,
      prev_pnl,
      prev_cash_flow,
      curr_starting_value,
      curr_starting_cash,
  ):
      self.prev_subperiod = PrevSubPeriodStats(
          returns=prev_returns, pnl=prev_pnl, cash_flow=prev_cash_flow
      )
  
      self.curr_subperiod = CurrSubPeriodStats(
          starting_value=curr_starting_value,
          starting_cash=curr_starting_cash,
      )
  
imports: from __future__ import division
  import logbook
  import numpy
  from collections import namedtuple
  from catalyst.assets import Future
  from six import itervalues, iteritems
  import catalyst.protocol
  from catalyst.constants import LOG_LEVEL
label_desc: Use image node_id 1 to create a new SubPeriodDivider object from inherited base classes: object with example: obj = SubPeriodDivider(prev_returns, prev_pnl, prev_cash_flow, curr_starting_value, curr_starting_cash)