Parent: $root.$constants
| kMongoReadModeNearest | Read mode 'nearest' |
| kMongoReadModePrimary | Read mode 'primary' |
| kMongoReadModePrimaryPreferred | Read mode 'primary preferred' |
| kMongoReadModeSecondary | Read mode 'secondary' |
| kMongoReadModeSecondaryPreferred | Read mode 'secondary preferred' |