void fillDocument() {
                for (var inherit : docTypeConfig.inherits()) {
                    var data = inProgressById.get(inherit.idx());
                    if (data == null) {
                        throw new IllegalArgumentException("Missing doctype for inherit idx: "+inherit.idx());
                    } else {
                        docType.inherit(data.docType);
                    }
                }
                Map<String, Collection<String>> fieldSets = new HashMap<>();
                for (var entry : docTypeConfig.fieldsets().entrySet()) {
                    fieldSets.put(entry.getKey(), entry.getValue().fields());
                }
                Set<String> importedFields = new HashSet<>();
                for (var imported : docTypeConfig.importedfield()) {
                    importedFields.add(imported.name());
                }
                docType.addFieldSets(fieldSets);
            }
One-shot configuration; should be called on a newly constructed manager
document/src/main/java/com/yahoo/document/DocumentTypeManagerConfigurer.java