duplicate keys in the mongo database
```
mongoengine.errors.NotUniqueError: Tried to save duplicate unique keys (E11000 duplicate key error collection: datasets_server_cache.splits index: dataset_name_1_config_name_1_split_name_1 dup key: { dataset_name: "csebuetnlp/xlsum", config_name: "chinese_traditional", split_name: "test" }, full error: {'index': 0, 'code': 11000, 'keyPattern': {'dataset_name': 1, 'config_name': 1, 'split_name': 1}, 'keyValue': {'dataset_name': 'csebuetnlp/xlsum', 'config_name': 'chinese_traditional', 'split_name': 'test'}, 'errmsg': 'E11000 duplicate key error collection: datasets_server_cache.splits index: dataset_name_1_config_name_1_split_name_1 dup key: { dataset_name: "csebuetnlp/xlsum", config_name: "chinese_traditional", split_name: "test" }'})
```
duplicate keys in the mongo database: ```
mongoengine.errors.NotUniqueError: Tried to save duplicate unique keys (E11000 duplicate key error collection: datasets_server_cache.splits index: dataset_name_1_config_name_1_split_name_1 dup key: { dataset_name: "csebuetnlp/xlsum", config_name: "chinese_traditional", split_name: "test" }, full error: {'index': 0, 'code': 11000, 'keyPattern': {'dataset_name': 1, 'config_name': 1, 'split_name': 1}, 'keyValue': {'dataset_name': 'csebuetnlp/xlsum', 'config_name': 'chinese_traditional', 'split_name': 'test'}, 'errmsg': 'E11000 duplicate key error collection: datasets_server_cache.splits index: dataset_name_1_config_name_1_split_name_1 dup key: { dataset_name: "csebuetnlp/xlsum", config_name: "chinese_traditional", split_name: "test" }'})
```