oneTimeKeys property
One-time keys for the queried devices. A map from user ID, to a
map from devices to a map from <algorithm>:<key_id>
to the key object.
See the key algorithms section for information on the Key Object format.
If necessary, the claimed key might be a fallback key. Fallback keys are re-used by the server until replaced by the device.
Implementation
Map<String, Map<String, Map<String, Object?>>> oneTimeKeys;