AI-generated Key Takeaways
- 
          AdUnitCodeError.Reason is an enumeration with reasons for errors related to ad unit codes. 
- 
          Valid characters for AdUnit.adUnitCode vary depending on the context, but generally include alphanumeric characters and various symbols. 
- 
          Specific codes are reserved and cannot be used for AdUnit.adUnitCode. 
- 
          The UNKNOWNvalue is returned for reasons not exposed in the requested API version.
- Namespace
- 
               https://www.google.com/apis/ads/publisher/v202502
| Enumeration | Description | 
|---|---|
| INVALID_CHARACTERS | For AdUnit.adUnitCode, only alpha-numeric characters, underscores, hyphens, periods, asterisks, double quotes, back slashes, forward slashes, exclamations, left angle brackets, colons and parentheses are allowed. | 
| INVALID_CHARACTERS_WHEN_UTF_CHARACTERS_ARE_ALLOWED | For AdUnit.adUnitCode, only letters, numbers, underscores, hyphens, periods, asterisks, double quotes, back slashes, forward slashes, exclamations, left angle brackets, colons and parentheses are allowed. | 
| INVALID_CHARACTERS_FOR_LEGACY_AD_EXCHANGE_TAG | For AdUnit.adUnitCode representing slot codes, only alphanumeric characters, underscores, hyphens, periods and colons are allowed. | 
| LEADING_FORWARD_SLASH | For AdUnit.adUnitCode, forward slashes are not allowed as the first character. | 
| RESERVED_CODE | Specific codes matching ca-*pub-*-tag are reserved for "Web Property IUs" generated as part of the SlotCode migration. | 
| UNKNOWN | The value returned if the actual value is not exposed by the requested API version. |