@Override
    public String toString() {
        return "(principal=" + (principal == null ? "<any>" : principal) +
               ", host=" + (host == null ? "<any>" : host) +
               ", operation=" + operation +
               ", permissionType=" + permissionType + ")";
    }
Returns a string describing an ANY or UNKNOWN field, or null if there is
no such field.
clients/src/main/java/org/apache/kafka/common/acl/AccessControlEntryData.java