code: def test_mmddrift(mmddrift_params):
      backend = mmddrift_params
      x_ref = np.random.randn(*(n, n_features)).astype("float32")
  
      try:
          cd = MMDDrift(x_ref=x_ref, backend=backend)
      except (NotImplementedError, ImportError):
          cd = None
  
      if backend.lower() == "pytorch":
          assert isinstance(cd._detector, MMDDriftTorch)
      elif backend.lower() == "tensorflow":
          assert isinstance(cd._detector, MMDDriftTF)
      elif backend.lower() == "keops" and has_keops:
          assert isinstance(cd._detector, MMDDriftKeops)
      else:
          assert cd is None
  
imports: import numpy
  import pytest
  from alibi_detect.cd import MMDDrift
  from alibi_detect.cd.pytorch.mmd import MMDDriftTorch
  from alibi_detect.cd.tensorflow.mmd import MMDDriftTF
  from alibi_detect.utils.frameworks import has_keops
label_desc: Use image node_id 2 for calling a global function with example usage: test_mmddrift(mmddrift_params) without return types