def test_invalid_scalar_index(adata, index):
    # https://github.com/theislab/anndata/issues/619
    with pytest.raises(IndexError, match=r".*index.* out of range\."):
        _ = adata[index]
def add_target_handle(self, layer):
        input_handle = layer.register_forward_hook(get_target_input)
        self.target_handle = input_handle