def next(self):
        """
        Returns the next attribute from the Instances object.

        :return: the next Attribute object
        :rtype: Attribute
        """
        if self.col < self.data.num_attributes:
            index = self.col
            self.col += 1
            return self.data.attribute(index)
        else:
            raise StopIteration()
Returns the next attribute from the Instances object.

        :return: the next Attribute object
        :rtype: Attribute