code: protected void appendSerialNumberIfSerializable(GenerationContext context, XtendTypeDeclaration source, JvmGenericType target) {
  		if (!target.isInterface() && this.inheritanceHelper.isSubTypeOf(target, Serializable.class, null)) {
  			appendSerialNumber(context, source, target);
  		}
  	}
docs: Append the serial number field if and only if the container type is serializable.
  
  <p>The serial number field is computed from the given context and from the generated fields.
  
  @param context the current generation context.
  @param source the source object.
  @param target the inferred JVM object.
  @see #appendSerialNumber(GenerationContext, XtendTypeDeclaration, JvmGenericType)