def is_labeled(G):
    """Returns True iff every edge in the graph `G`
    has the attribute ``label``.

    Parameters
    ----------
    G : graph

    Examples
    --------
    >>> G = nx.MultiDiGraph()
    >>> G.add_edge(1, 2, label="a")
    >>> sd.is_labeled(G)
    True
    >>> G.add_edge(2, 1)
    >>> sd.is_labeled(G)
    False

    """
    return all("label" in data for _, _, data in G.edges(data=True))