Purchase a Reserved Instance for use with your account.
        ** CAUTION **
        This request can result in large amounts of money being charged to your
        AWS account.  Use with caution!

        :type reserved_instances_offering_id: string
        :param reserved_instances_offering_id: The offering ID of the Reserved
                                               Instance to purchase

        :type instance_count: int
        :param instance_count: The number of Reserved Instances to purchase.
                               Default value is 1.

        :rtype: :class:`boto.ec2.reservedinstance.ReservedInstance`
        :return: The newly created Reserved Instance

def purchase_reserved_instance_offering(self,
                                            reserved_instances_offering_id,
                                            instance_count=1):
        """
        Purchase a Reserved Instance for use with your account.
        ** CAUTION **
        This request can result in large amounts of money being charged to your
        AWS account.  Use with caution!

        :type reserved_instances_offering_id: string
        :param reserved_instances_offering_id: The offering ID of the Reserved
                                               Instance to purchase

        :type instance_count: int
        :param instance_count: The number of Reserved Instances to purchase.
                               Default value is 1.

        :rtype: :class:`boto.ec2.reservedinstance.ReservedInstance`
        :return: The newly created Reserved Instance
        """
        params = {
            'ReservedInstancesOfferingId' : reserved_instances_offering_id,
            'InstanceCount' : instance_count}
        return self.get_object('PurchaseReservedInstancesOffering', params,
                               ReservedInstance, verb='POST')