def get_unobs_nd_names(gname):
    """
    For a graph named gname, this method returns a list of the names of its
    unobserved nodes (i.e., either [], or ["U"] or ["U1", "U2"])

    Parameters
    ----------
    gname : str

    Returns
    -------
    list[str]

    """
    if gname in ["G2", "G3", "G5", "G6", "G10", "G11u", "G15", "G16"]:
        li = ["U"]
    elif gname in ["G7", "G7up"]:
        li = ["U1", "U2"]
    else:
        li = []
    return li