code: def test_assemble_block_zero_sig():
      df = pd.DataFrame(
          {
              "mu": [0.2, 0],
              "sig": [0.1, 0],
              "values": [[0.1, 0.3], [0, 0]],
          }
      )
      with pytest.raises(ValueError):
          assemble_block(
              n_rows=2,
              n_cols=2,
              pdf=df,
              cov_matrix=np.array([]),
              row_mask=np.array([]),
          )
  
imports: from glow.wgr.model_functions import *
  from glow.wgr.model_functions import _prepare_covariates, _prepare_labels_and_warn
  import math
  import numpy
  import pandas
  from pyspark.sql import Row
  import pytest
  from sklearn.linear_model import LogisticRegression
  from sklearn.datasets import load_breast_cancer
label_desc: Use image node_id 5 for calling a global function with example usage: test_assemble_block_zero_sig() without return types