private static UnsupportedOperationException createUnsupportedException(String aspect) {
        return new UnsupportedOperationException("'" + aspect + "' is not meaningful or relevant for an imported field.");
    }
Returns a field representation of the imported field.
Changes to the returned instance are not propagated back to the underlying imported field!
config-model/src/main/java/com/yahoo/schema/document/ImmutableImportedSDField.java