Context._instance is back to a class method
Context._instance is back to a class method

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