The index of the product custom attribute.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v24/enums/product_custom_attribute_index.proto)

| Enums ||
|---|---|
| ## `INDEX0` | First product custom attribute. |
| ## `INDEX1` | Second product custom attribute. |
| ## `INDEX2` | Third product custom attribute. |
| ## `INDEX3` | Fourth product custom attribute. |
| ## `INDEX4` | Fifth product custom attribute. |
| ## `UNKNOWN` | Used for return value only. Represents value unknown in this version. |
| ## `UNSPECIFIED` | Not specified. |