private static void exportFieldSetDefinition(Set<FieldSet> fieldSets, Writer out, int ind) throws IOException {
        out.write(ind(ind) + "java.util.Map<java.lang.String, java.util.Collection<java.lang.String>> fieldSets = new java.util.HashMap<>();\n");
        for (FieldSet fieldSet : fieldSets) {
            out.write(ind(ind) + "fieldSets.put(\"" + fieldSet.getName() + "\", java.util.List.of(");
            int count = 0;
            for (String field : fieldSet.getFieldNames()) {
                out.write("\"" + field + "\"");
                if (++count != fieldSet.getFieldNames().size()) {
                    out.write(",");
                }
            }
            out.write("));\n");
        }
        out.write(ind(ind) + "ret.addFieldSets(fieldSets);\n");
    }
\n"+
                ind(ind)+" * Constructs a "+className+" by taking a deep copy of the provided StructuredFieldValue.\n" +
                ind(ind)+"
vespa-documentgen-plugin/src/main/java/com/yahoo/vespa/DocumentGenMojo.java