def METHOD_NAME(G):
    """
    Returns True if `G` is an arborescence.
    An arborescence is a directed tree with maximum in-degree equal to 1.
    Parameters
    ----------
    G : graph
        The graph to test.
    Returns
    -------
    b : bool
        A boolean that is True if `G` is an arborescence.
    Examples
    --------
    >>> G = nx.DiGraph([(0, 1), (0, 2), (2, 3), (3, 4)])
    >>> nx.is_arborescence(G)
    True
    >>> G.remove_edge(0, 1)
    >>> G.add_edge(1, 2)  # maximum in-degree is 2
    >>> nx.is_arborescence(G)
    False
    Notes
    -----
    In another convention, an arborescence is known as a *tree*.
    See Also
    --------
    is_tree
    """
    return is_tree(G) and max(d for n, d in G.in_degree()) <= 1