Describe the bug
Not sure if this would be considered part of the API, but the toString of most objects in this project is fairly consistent in that it outputs human readable values.
This used to be the case for Field too until version 24/25 where the DirectivesHolder was introduced.

public String toString() {
    return "Field{" +
            "name='" + name + '\'' +
            ", alias='" + alias + '\'' +
            ", arguments=" + arguments +
            ", directives=" + directives + // <- used to be a List<Directive> now is DirectivesHolder
            ", selectionSet=" + selectionSet +
            '}';
}

Because DirectivesHolder doesn't have a toString implementation, if you write any object containing it to a log for example, it will result in something like:

SelectionSet{selections=[Field{name='description', alias='null', arguments=[], directives=graphql.language.NodeUtil$DirectivesHolder@64e8d216, selectionSet=null}]}

Would be nice if this were to be fixed.