code: def test_blob_usage_errors(backend):
      with backend() as be:
          run_sampler(be, blobs=True)
          with pytest.raises(ValueError):
              run_sampler(be, blobs=False)
  
      with backend() as be:
          run_sampler(be, blobs=False)
          with pytest.raises(ValueError):
              run_sampler(be, blobs=True)
  
file_path: emcee/src/emcee/tests/unit/test_backends.py
imports: import os
  from itertools import product
  from os.path import join
  import numpy
  import pytest
  from emcee import EnsembleSampler, State, backends
  from emcee.backends.hdf import does_hdf5_support_longdouble
label_desc: Use image node_id 7 for calling a global function with example usage: test_blob_usage_errors(backend) without return types