docstr: confirm that the right number of riskmetrics were calculated for each
  window length.
docstr_tok: ["confirm","that","the","right","number","of","riskmetrics","were","calculated","for","each","window","length","."]
code: def check_metrics(self, metrics, total_months, start_date):
      """
      confirm that the right number of riskmetrics were calculated for each
      window length.
      """
      for period, length in zip(PERIODS, [1, 3, 6, 12]):
          self.assert_range_length(
              metrics[period], total_months, length, start_date
          )
  
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 16 for calling the TestRisk obj's underlying member method code with example usage: obj.check_metrics(metrics, total_months, start_date) without return types