def list_driver_connections(graph, driver=True):
    """Return all edges that are driver connections, i.e.,
    (params, objectives,constraints).  If driver contains the
    name of a specific driver, then only return connections for
    that driver.
    """
    if driver is True:
        return [(u,v) for u,v,data in graph.edges_iter(data=True)
                            if data.get('drv_conn')]
    else:
        return [(u,v) for u,v,data in graph.edges_iter(data=True)
                            if data.get('drv_conn')==driver]