'Constructor.'

def __init__(self, operand, **kwargs):

    super(UnaryOperator, self).__init__(arguments=[operand], **kwargs)
    if (len(self.args) != 1):
        raise InvalidNumberOfOperands(('Only    one    operand    is    accepted    by    %s.    Received    %d.' % (self.__class__.__name__, len(self.args))))
