NextKeys: StorageDescriptor<[Key: SS58String], {
authority_discovery: FixedSizeBinary<32>;
babe: FixedSizeBinary<32>;
beefy: FixedSizeBinary<33>;
grandpa: FixedSizeBinary<32>;
para_assignment: FixedSizeBinary<32>;
para_validator: FixedSizeBinary<32>;
}, true, never>
The next session keys for a validator.