@Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof SpanTree tree)) return false;

        if (!annotationsEquals(tree)) return false;
        if (!name.equals(tree.name)) return false;
        if (!root.equals(tree.root)) return false;

        return true;
    }
Returns the StringFieldValue that this SpanTree belongs to.

@return the StringFieldValue that this SpanTree belongs to, if any, otherwise null.
document/src/main/java/com/yahoo/document/annotation/SpanTree.java