code: def _get_matrix():
      mat = random(
          100, 100, density=0.5, format="csr", dtype=np.float32
      )
      return mat.tocoo()
  
file_path: implicit/tests/evaluation_test.py
imports: import numpy
  import pytest
  from scipy.sparse import csr_matrix, random
  import implicit
  from implicit.evaluation import leave_k_out_split, precision_at_k, train_test_split
  from implicit.datasets.movielens import get_movielens
label_desc: Use image node_id 2 for calling a global function with example usage: _get_matrix() and returns: mat