AI-generated Key Takeaways
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          The content describes an enum for field mask errors. 
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          Possible errors include missing or disallowed field masks, or issues with specific fields like unknown fields or attempting to update fields with subfields incorrectly. 
Enum describing possible field mask errors.
| Enums | |
|---|---|
| 
 | Enum unspecified. | 
| 
 | The received error code is not known in this version. | 
| 
 | The field mask must be provided for update operations. | 
| 
 | The field mask must be empty for create and remove operations. | 
| 
 | The field mask contained an invalid field. | 
| 
 | The field mask updated a field with subfields. Fields with subfields may be cleared, but not updated. To fix this, the field mask should select all the subfields of the invalid field. |