availability_cores: RuntimeDescriptor<[], Enum<{
    Free: undefined;
    Occupied: {
        availability: {
            bitsLen: number;
            bytes: Uint8Array;
        };
        candidate_descriptor: {
            core_index: number;
            erasure_root: FixedSizeBinary<32>;
            para_head: FixedSizeBinary<32>;
            para_id: number;
            persisted_validation_data_hash: FixedSizeBinary<32>;
            pov_hash: FixedSizeBinary<32>;
            relay_parent: FixedSizeBinary<32>;
            reserved1: FixedSizeBinary<25>;
            reserved2: FixedSizeBinary<64>;
            session_index: number;
            validation_code_hash: FixedSizeBinary<32>;
            version: number;
        };
        candidate_hash: FixedSizeBinary<32>;
        group_responsible: number;
        next_up_on_available?: {
            collator?: FixedSizeBinary<(...)>;
            para_id: number;
        };
        next_up_on_time_out?: {
            collator?: FixedSizeBinary<(...)>;
            para_id: number;
        };
        occupied_since: number;
        time_out_at: number;
    };
    Scheduled: {
        collator?: FixedSizeBinary<32>;
        para_id: number;
    };
}>[]>

Yields information on all availability cores as relevant to the child block. Cores are either free or occupied. Free cores can have paras assigned to them.