session_info: RuntimeDescriptor<[index: number], {
    active_validator_indices: number;
    assignment_keys: FixedSizeBinary<32>;
    discovery_keys: FixedSizeBinary<32>;
    dispute_period: number;
    n_cores: number;
    n_delay_tranches: number;
    needed_approvals: number;
    no_show_slots: number;
    random_seed: FixedSizeBinary<32>;
    relay_vrf_modulo_samples: number;
    validator_groups: number;
    validators: FixedSizeBinary<32>;
    zeroth_delay_tranche_width: number;
} | undefined>

Get the session info for the given session, if stored.

NOTE: This function is only available since parachain host version 2.