@Override
    public boolean hasSingleAttribute() {
        if (getAttributes().size() != 1) {
            return false;
        }
        // Must use the name of the target field as the attributes also exist on the target field.
        return (getAttributes().get(importedField.targetField().getName()) != null);
    }
Wraps {@link ImportedField} as {@link ImmutableSDField}.
Methods that are not meaningful or relevant for imported fields will throw {@link UnsupportedOperationException}.

@author bjorncs
config-model/src/main/java/com/yahoo/schema/document/ImmutableImportedSDField.java