removed _string refs
removed _string refs

yyt030/pyzmq,caidongyun/pyzmq,Mustard-Systems-Ltd/pyzmq,Mustard-Systems-Ltd/pyzmq,yyt030/pyzmq,swn1/pyzmq,caidongyun/pyzmq,swn1/pyzmq,yyt030/pyzmq,swn1/pyzmq,caidongyun/pyzmq,ArvinPan/pyzmq,dash-dash/pyzmq,Mustard-Systems-Ltd/pyzmq,dash-dash/pyzmq,ArvinPan/pyzmq,ArvinPan/pyzmq,dash-dash/pyzmq