code: def test_mv_feature_functions():
      """test feature functions with multivariate data"""
  
      # sliding window data is shape [n_segments, width, variables]
      N = 20
      W = 30
      mv_data = np.random.rand(N, W, 3)
  
      ftr_funcs = {}
      ftr_funcs.update(feature_functions.all_features())
      ftr_funcs.update(feature_functions.base_features())
      ftr_funcs.update(feature_functions.hudgins_features())
      ftr_funcs.update(feature_functions.emg_features())
  
      for f in ftr_funcs:
          mvf = ftr_funcs[f](mv_data)
          assert len(mvf) == N
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_mv_feature_functions() without return types