code: def test_representation(self):
      test_period = ClassicRiskMetrics.risk_metric_period(
          start_session=self.start_session,
          end_session=self.end_session,
          algorithm_returns=self.algo_returns,
          benchmark_returns=self.benchmark_returns,
          algorithm_leverages=pd.Series(
              0.0, index=self.algo_returns.index
          ),
      )
      metrics = {
          "algorithm_period_return",
          "benchmark_period_return",
          "treasury_period_return",
          "period_label",
          "excess_return",
          "trading_days",
          "benchmark_volatility",
          "algo_volatility",
          "sharpe",
          "sortino",
          "beta",
          "alpha",
          "max_drawdown",
          "max_leverage",
      }
  
      self.assertEqual(set(test_period), metrics)
  
imports: import datetime
  import pandas
  import numpy
  from zipline.utils import factory
  from zipline.finance.trading import SimulationParameters
  import zipline.testing.fixtures
  from zipline.finance.metrics import _ClassicRiskMetrics
label_desc: Use image node_id 22 for calling the TestRisk obj's underlying member method code with example usage: obj.test_representation() without return types