(self, msg, key)
Returns a digital signature for the specified message
        using the specified key value.
Returns a digital signature for the specified message
        using the specified key value.
Returns a digital signature for the specified message using the specified key value .
def sign(self, msg, key):
        """
        Returns a digital signature for the specified message
        using the specified key value.
        """
        raise NotImplementedError
def sign ( self , msg , key ) : raise NotImplementedError