Function pallet_session::historical::offchain::prove_session_membership

pub fn prove_session_membership<T: Config, D: AsRef<[u8]>>(
    session_index: SessionIndex,
    session_key: (KeyTypeId, D)
) -> Option<MembershipProof>

Create a proof based on the data available in the off-chain database.

Based on the yielded MembershipProof the implementer may decide what to do, i.e. in case of a failed proof, enqueue a transaction back on chain reflecting that, with all its consequences such as i.e. slashing.