AI-generated Key Takeaways
- 
          The document provides an enumeration of possible errors related to campaign feeds. 
- 
          Errors include issues with existing feeds, removed feeds, invalid placeholder types, and missing feed mappings. 
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          Some campaign feed operations are restricted for removed or legacy feed types. 
Enum describing possible campaign feed errors.
| Enums | |
|---|---|
| 
 | Enum unspecified. | 
| 
 | The received error code is not known in this version. | 
| 
 | An active feed already exists for this campaign and placeholder type. | 
| 
 | The specified feed is removed. | 
| 
 | The CampaignFeed already exists. UPDATE should be used to modify the existing CampaignFeed. | 
| 
 | Cannot update removed campaign feed. | 
| 
 | Invalid placeholder type. | 
| 
 | Feed mapping for this placeholder type does not exist. | 
| 
 | Location CampaignFeeds cannot be created unless there is a location CustomerFeed for the specified feed. | 
| 
 | Feed is read only. |