class_docstr: Tracks the performance of the algorithm.
code: def process_close_position(self, asset, dt, data_portal):
      txn = (
          self.position_tracker.maybe_create_close_position_transaction(
              asset, dt, data_portal
          )
      )
      if txn:
          self.process_transaction(txn)
  
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 16 for calling the PerformanceTracker obj's underlying member method code with example usage: obj.process_close_position(asset, dt, data_portal) without return types