n_tasks = 1// Test case where some weights are zero (i.e. masked)X = np.ones(n_samples)
y = np.zeros((n_samples, n_tasks))
y[:n_positives] = 1
w = np.ones((n_samples, n_tasks))
// Set half the positives to have zero weight
w[:n_positives // 2] = 0dataset = dc.data.NumpyDataset(X, y, w)
stratified_splitter = dc.splits.RandomStratifiedSplitter()
train, valid, test = stratified_splitter.split(dataset, 0.5, 0, 0.5)// There are 10 nonzero actives.// The split index should partition this into half, so expect 5
w_present = (w != 0)