Receive a 'picture' message from the socket (or actor). This is a
va_list version of zsock_recv (), so please consult its documentation
for the details.

def vrecv(self, picture, argptr):
        """
        Receive a 'picture' message from the socket (or actor). This is a
va_list version of zsock_recv (), so please consult its documentation
for the details.
        """
        return lib.zsock_vrecv(self._as_parameter_, picture, argptr)