code: def __init__(self, data_frequency):
      # asset => position object
      self.positions = positiondict()
      self._unpaid_dividends = {}
      self._unpaid_stock_dividends = {}
      self._positions_store = zp.Positions()
  
      self.data_frequency = data_frequency
  
imports: from __future__ import division
  import logbook
  import numpy
  from collections import namedtuple
  from math import isnan
  from six import iteritems, itervalues
  from catalyst.finance.performance.position import Position
  from catalyst.finance.transaction import Transaction
  from catalyst.utils.input_validation import expect_types
  import catalyst.protocol
  from catalyst.assets import Future, Asset
  from .position import positiondict
  from catalyst.constants import LOG_LEVEL
label_desc: Use image node_id 1 to create a new PositionTracker object from inherited base classes: object with example: obj = PositionTracker(data_frequency)