Parent: $root.$constants
| kMongoReadConcernAvailable | Read concern is set to "available" |
| kMongoReadConcernLinearizable | Read concern is set to "linearizable" |
| kMongoReadConcernLocal | Read concern is set to "local" |
| kMongoReadConcernMajority | Read concern is set to "majority" |
| kMongoReadConcernNotSet | Read concern is not set |
| kMongoReadConcernSnapshot | Read concern is set to "snapshot" |