GTIN Product ID Exception

[200317314]

I am listing a product that does not have a UPC or ASIN and I have a GTIN exception.

I want to know how to add this as an attribute or a feed that allows me to use the exception via code
I do see this but im not sure how to add it
<xsd:element ref="StandardProductID" minOccurs="0"/> <xsd:element name="GtinExemptionReason" minOccurs="0"> <xsd:simpleType> <xsd:restriction base="xsd:string"> <xsd:enumeration value="bundle"/> <xsd:enumeration value="part"/> </xsd:restriction> </xsd:simpleType> </xsd:element>

I am adding my attributes to a ListingItemPutRequest() like this

attrs.Add("product_description", new object[] { new { language_tag = "en_CA", value = "Really cool throwable dog toy", marketplace_id = FikaAmazonAPI.Utils.MarketPlace.Canada.ID } });

When I add my item I get this error

How can I add a product ID as null so I can use the GTIN exception?