@Override
    public ImmutableSDField getStructField(String name) {
        ImportedField field = importedComplexField.getNestedField(name);
        return (field != null) ? field.asImmutableSDField() : null;
    }
Wraps {@link ImportedComplexField} as {@link ImmutableSDField}.
config-model/src/main/java/com/yahoo/schema/document/ImmutableImportedComplexSDField.java