def update_nonce(input_params):
        '''
        Static method to return a copy of the input dictionary with an
        additional unique nonce
        :param input: an input dictionary that may be empty
        :type input: dict
        :returns an extended copy of the input with an additional nonce field

        The input dictionary is updated with a nonce only if does not already
        have a non empty nonce
        '''
        input_cp = input_params.copy()
        if len(input_cp.get('nonce', '')) == 0:
            input_cp['nonce'] = str(Nonce())
        return input_cp
Static method to return a copy of the input dictionary with an
        additional unique nonce
        :param input: an input dictionary that may be empty
        :type input: dict
        :returns an extended copy of the input with an additional nonce field

        The input dictionary is updated with a nonce only if does not already
        have a non empty nonce