Enum describing possible list operation errors.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v26/errors/list_operation_error.proto)

| Enums ||
|---|---|
| ## `DUPLICATE_VALUES` | Duplicate or identical value is sent in multiple list operations. |
| ## `REQUIRED_FIELD_MISSING` | Field required in value is missing. |
| ## `UNKNOWN` | The received error code is not known in this version. |
| ## `UNSPECIFIED` | Enum unspecified. |