code: def test_knn_graph_change(self, issue_manager):
      dist_matrix = np.random.randint(1, 5, size=(10, 10))
      np.fill_diagonal(
          dist_matrix, 0
      )  # Make diagonal 0 to mimic distance matrix
      knn_graph = sp.csr_matrix(dist_matrix)
      nnz_before_clustering = knn_graph.nnz
      issue_manager.perform_clustering(knn_graph)
      nnz_after_clustering = knn_graph.nnz
      assert nnz_before_clustering == nnz_after_clustering
  
file_path: cleanlab/tests/datalab/issue_manager/test_underperforming_group.py
imports: import numpy
  import pytest
  import pandas
  import scipy.sparse
  from cleanlab.datalab.internal.issue_manager.underperforming_group import UnderperformingGroupIssueManager
  from sklearn.datasets import make_blobs, load_iris
label_desc: Use image node_id 11 for calling the TestUnderperformingGroupIssueManager obj's underlying member method code with example usage: obj.test_knn_graph_change(issue_manager) without return types