reverse operator function
        :param f: operator.add/sub/mul... used operator
        :param x: other object field should be add/sub... with
        :return: dictionary (same shape as field.d) with result of operation

def __rmath(self, f, x):
        """reverse operator function
        :param f: operator.add/sub/mul... used operator
        :param x: other object field should be add/sub... with
        :return: dictionary (same shape as field.d) with result of operation
        """

        d = {}
        if isinstance(x, (int, long, float, complex)):
            for i in self.__d: d[i] = f(x , self.__d[i])
        else: raise ValueError('Cannot execute reverse operator, only (int, float, complex) as first operand possible')

        return d