code: def position_tracker(self):
      return self._position_tracker
  
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 3 for calling the PerformancePeriod obj's underlying member method code with example usage: obj.position_tracker() and returns: self