code: def test_restart(backend):
      with backend() as be:
          sampler = run_sampler(be, nsteps=0)
          with pytest.raises(ValueError):
              sampler.run_mcmc(None, 10)
  
          sampler = run_sampler(be)
          sampler.run_mcmc(None, 10)
  
      with backend() as be:
          sampler = run_sampler(be, store=False)
          sampler.run_mcmc(None, 10)
  
imports: import pickle
  from itertools import islice, product
  import numpy
  import pytest
  from emcee import EnsembleSampler, backends, moves, walkers_independent
label_desc: Use image node_id 7 for calling a global function with example usage: test_restart(backend) without return types