code: def make_filter_string(cls, filter_specification):
          
          registry = get_current_registry()
          visitor_cls = registry.getUtility(IFilterSpecificationVisitor,
                                            name=EXPRESSION_KINDS.CQL)
          visitor = visitor_cls()
          filter_specification.accept(visitor)
          return str(visitor.expression)
docs: Converts the given filter specification to a CQL filter expression.