code: def test_bad_parallel_methods(self, ts_short, backend):
      m = Prophet(stan_backend=backend)
      m.fit(ts_short)
      # invalid alias
      with pytest.raises(ValueError, match="'parallel' should be one"):
          diagnostics.cross_validation(
              m, horizon="4 days", parallel="bad"
          )
      # no map method
      with pytest.raises(ValueError, match="'parallel' should be one"):
          diagnostics.cross_validation(
              m, horizon="4 days", parallel=object()
          )
  
imports: import datetime
  import itertools
  import numpy
  import pandas
  import pytest
  from prophet import Prophet, diagnostics
label_desc: Use image node_id 2 for calling the TestCrossValidation obj's underlying member method code with example usage: obj.test_bad_parallel_methods(ts_short, backend) without return types