Adds `max` operator that specifies upper bound for specific index.

        :Parameters:
          - `spec`: a list of field, limit pairs specifying the exclusive
            upper bound for all keys of a specific index in order.

        .. versionadded:: 2.7

def max(self, spec):
        """Adds `max` operator that specifies upper bound for specific index.

        :Parameters:
          - `spec`: a list of field, limit pairs specifying the exclusive
            upper bound for all keys of a specific index in order.

        .. versionadded:: 2.7
        """
        if not isinstance(spec, (list, tuple)):
            raise TypeError("spec must be an instance of list or tuple")

        self.__check_okay_to_chain()
        self.__max = SON(spec)
        return self