(self, func)
set function to create musk key. You can custumize mask key generator.
        Mainly, this is for testing purpose.

        func: callable object. the fuct must 1 argument as integer.
              The argument means length of mask key.
              This func must be return string(byte array),
              which length is argument specified.
set function to create musk key. You can custumize mask key generator.
        Mainly, this is for testing purpose.
set function to create musk key . You can custumize mask key generator . Mainly this is for testing purpose .
def set_mask_key(self, func):
        """
        set function to create musk key. You can custumize mask key generator.
        Mainly, this is for testing purpose.

        func: callable object. the fuct must 1 argument as integer.
              The argument means length of mask key.
              This func must be return string(byte array),
              which length is argument specified.
        """
        self.get_mask_key = func
def set_mask_key ( self , func ) : self . get_mask_key = func