def test_view_of_view(matrix_type, subset_func, subset_func2):
    adata = gen_adata((30, 15), X_type=matrix_type)
    adata.raw = adata
    if subset_func is single_subset:
        pytest.xfail("Other subset generating functions have trouble with this")
    var_s1 = subset_func(adata.var_names, min_size=4)
    var_view1 = adata[:, var_s1]
    var_s2 = subset_func2(var_view1.var_names)
    var_view2 = var_view1[:, var_s2]
    assert var_view2._adata_ref is adata
    obs_s1 = subset_func(adata.obs_names, min_size=4)
    obs_view1 = adata[obs_s1, :]
    obs_s2 = subset_func2(obs_view1.obs_names)
    assert adata[obs_s1, :][:, var_s1][obs_s2, :]._adata_ref is adata

    view_of_actual_copy = adata[:, var_s1].copy()[obs_s1, :].copy()[:, var_s2].copy()

    view_of_view_copy = adata[:, var_s1][obs_s1, :][:, var_s2].copy()

    assert_equal(view_of_actual_copy, view_of_view_copy, exact=True)
def _add_implementor(rpc_code, blocking, fn):

    # Validate the argument types.
    if type(rpc_code) is not int:
        raise TypeError("Expected int, got %r instead" % type(rpc_code))
    if type(blocking) is not bool:
        raise TypeError("Expected bool, got %r instead" % type(blocking))
    if not callable(fn):
        raise TypeError("Expected callable, got %r instead" % type(fn))

    # Validate the RPC code.
    if rpc_code in rpcMap:
        try:
            msg = "Duplicated RPC implementors for code %d: %s and %s"
            msg %= (rpc_code, rpcMap[rpc_code][0].__name__, fn.__name__)
        except Exception:
            msg = "Duplicated RPC implementors for code: %d" % rpc_code
        raise SyntaxError(msg)

    # TODO: use introspection to validate the function signature

    # Register the implementor.
    rpcMap[rpc_code] = (fn, blocking)

    # Return the implementor. No wrapping is needed! :)
    return fn