public static AbstractServerPredicate alwaysTrue() {
        return new AbstractServerPredicate() {        
            @Override
            public boolean apply(@Nullable PredicateKey input) {
                return true;
            }
        };
    }
A basic building block for server filtering logic which can be used in rules and server list filters.
The input object of the predicate is {@link PredicateKey}, which has Server and load balancer key
information. Therefore, it is possible to develop logic to filter servers by both Server and load balancer
key or either one of them. 

@author awang
ribbon-loadbalancer/src/main/java/com/netflix/loadbalancer/AbstractServerPredicate.java