public Collection<SpanTree> getSpanTrees() {
        if (spanTrees == null) {
            return List.of();
        }
        return List.copyOf(spanTrees.values());
    }
Returns an unmodifiable Collection of the span trees with annotations over this String, if any.

@return an unmodifiable Collection of the span trees with annotations over this String, or an empty Collection
document/src/main/java/com/yahoo/document/datatypes/StringFieldValue.java