Converts the given order specification to a CQL order expression.

def make_order_string(cls, order_specification):
        """
        Converts the given order specification to a CQL order expression.
        """
        registry = get_current_registry()
        visitor_cls = registry.getUtility(IOrderSpecificationVisitor,
                                          name=EXPRESSION_KINDS.CQL)
        visitor = visitor_cls()
        order_specification.accept(visitor)
        return str(visitor.expression)