def METHOD_NAME(mrcs_data):
    src = ImageSource.from_file(
        f"{DATA_FOLDER}/toy_projections.mrcs",
        indices=np.array([0, 1, 5, 304]),
        lazy=False,
    )
    assert src.shape == (4, 30, 30)  # Not (100, 30, 30)
    for i, (indices, chunk) in enumerate(src.chunks(chunksize=2)):
        assert len(indices) == chunk.shape[0]
        if i == 0:
            assert torch.allclose(mrcs_data[np.array([0, 1]), :, :], chunk)
        elif i == 1:
            assert torch.allclose(mrcs_data[np.array([5, 304]), :, :], chunk)