code: def test_cross_validation_custom_cutoffs(self, ts_short, backend):
      m = Prophet(stan_backend=backend)
      m.fit(ts_short)
      # When specify a list of cutoffs
      #  the cutoff dates in df_cv are those specified
      df_cv1 = diagnostics.cross_validation(
          m,
          horizon="32 days",
          period="10 days",
          cutoffs=[
              pd.Timestamp("2012-07-31"),
              pd.Timestamp("2012-08-31"),
          ],
      )
      assert len(df_cv1["cutoff"].unique()) == 2
  
imports: import datetime
  import itertools
  import numpy
  import pandas
  import pytest
  from prophet import Prophet, diagnostics
label_desc: Use image node_id 8 for calling the TestCrossValidation obj's underlying member method code with example usage: obj.test_cross_validation_custom_cutoffs(ts_short, backend) without return types