code: def _assert_disjoint(x, y):
      x = x.tocsr()
      y = y.tocoo()
  
      for i, j in zip(y.row, y.col):
          assert x[i, j] == 0.0
  
imports: import pytest
  from lightfm.cross_validation import random_train_test_split
  from lightfm.datasets import fetch_movielens
label_desc: Use image node_id 1 for calling a global function with example usage: _assert_disjoint(x, y) without return types