def drop_disjoint(train, test):
    in_training = find(train.sum(0).A.flatten() != 0)
    train = train[:, in_training]
    test = test[:, in_training]
    in_test = find(test.sum(0).A.flatten() != 0)
    train = train[:, in_test]
    test = test[:, in_test]
    return sparse.vstack((train, test)).tocsr()
Removes all features from train and test that are strictly all 0 in either the train
dataset/ETHPy150Open theusual/kaggle-seeclickfix-ensemble/Miroslaw/data_transforms.py/drop_disjoint