def _port_to_urn(dpid, port):
    
    return "%s+port:%s" % (_dpid_to_urn(dpid), port)
get sum from internal histogram
dataset/ETHPy150Open fp7-ofelia/ocf/expedient/src/python/plugins/openflow/plugin/gapi/rspec.py/_port_to_urn--crossover with--dataset/ETHPy150Open omergertel/pyformance/pyformance/meters/timer.py/Timer.get_sum