code: def test_vectorize():
      def lp_vec(p):
          return -0.5 * np.sum(p**2, axis=1)
  
      np.random.seed(42)
      nwalkers, ndim = 32, 3
      coords = np.random.randn(nwalkers, ndim)
      sampler = EnsembleSampler(nwalkers, ndim, lp_vec, vectorize=True)
      sampler.run_mcmc(coords, 10)
  
      assert sampler.get_chain().shape == (10, nwalkers, ndim)
  
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 8 for calling a global function with example usage: test_vectorize() and returns: unknown