code: def test_check_single_cutoff_forecast_func_calls(
      self, ts_short, monkeypatch, backend
  ):
      m = Prophet(stan_backend=backend)
      m.fit(ts_short)
  
      def mock_predict(df, model, cutoff, horizon, predict_columns):
          nonlocal n_calls
          n_calls = n_calls + 1
          return pd.DataFrame(
              {
                  "ds": pd.date_range(start="2012-09-17", periods=3),
                  "yhat": np.arange(16, 19),
                  "yhat_lower": np.arange(15, 18),
                  "yhat_upper": np.arange(17, 20),
                  "y": np.arange(16.5, 19.5),
                  "cutoff": [datetime.date(2012, 9, 15)] * 3,
              }
          )
  
      monkeypatch.setattr(
          diagnostics, "single_cutoff_forecast", mock_predict
      )
      # cross validation  with 3 and 7 forecasts
      for args, forecasts in (
          (["4 days", "10 days", "115 days"], 3),
          (["4 days", "4 days", "115 days"], 7),
      ):
          n_calls = 0
          _ = diagnostics.cross_validation(m, *args)
          # check single forecast function called expected number of times
          assert n_calls == forecasts
  
imports: import datetime
  import itertools
  import numpy
  import pandas
  import pytest
  from prophet import Prophet, diagnostics
label_desc: Use image node_id 3 for calling the TestCrossValidation obj's underlying member method code with example usage: obj.test_check_single_cutoff_forecast_func_calls(ts_short, monkeypatch, backend) and returns: pd