code: def test_nonparallelized_chains_are_random(self):
      with pm.Model() as model:
          x = pm.Normal("x", 0, 1)
          for stepper in TestPopulationSamplers.steppers:
              step = stepper()
              idata = pm.sample(
                  chains=4,
                  cores=1,
                  draws=20,
                  tune=0,
                  step=DEMetropolis(),
                  compute_convergence_checks=False,
              )
              samples = idata.posterior["x"].values[:, 5]
  
              assert (
                  len(set(samples)) == 4
              ), f"Parallelized {stepper} chains are identical."
  
file_path: pymc/tests/sampling/test_population.py
imports: import pytest
  import pymc
  from pymc.step_methods.metropolis import DEMetropolis
label_desc: Use image node_id 3 for calling the TestPopulationSamplers obj's underlying member method code with example usage: obj.test_nonparallelized_chains_are_random() without return types