class_docstr: Tracks the performance of the algorithm.
code: def update_performance(self):
      # calculate performance as of last trade
      self.cumulative_performance.calculate_performance()
      self.todays_performance.calculate_performance()
  
imports: from __future__ import division
  import logbook
  import pandas
  from pandas.tseries.tools import normalize_date
  from catalyst.finance.performance.period import PerformancePeriod
  from catalyst.errors import NoFurtherDataError
  import catalyst.finance.risk
  from .position_tracker import PositionTracker
  from catalyst.constants import LOG_LEVEL
label_desc: Use image node_id 6 for calling the PerformanceTracker obj's underlying member method code with example usage: obj.update_performance() without return types