AI-generated Key Takeaways
- 
          This operation allows for the creation or updating of a single conversion custom variable. 
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          The update_maskfield is used to specify which fields of the resource are modified during an update operation.
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          The operationfield determines the type of mutate operation, which can be eithercreateorupdate.
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          When creating, no resource name is expected, but when updating, a valid resource name is required for the conversion custom variable. 
A single operation (create, update) on a conversion custom variable.
| Fields | |
|---|---|
| 
 | FieldMask that determines which resource fields are modified in an update. | 
| Union field 
 | |
| 
 | Create operation: No resource name is expected for the new conversion custom variable. | 
| 
 | Update operation: The conversion custom variable is expected to have a valid resource name. |