Function is_member_of_association_state 

pub async fn is_member_of_association_state<Client>(
    api_client: &ApiClientWrapper<Client>,
    inbox_id: &str,
    identifier: &MemberIdentifier,
    scw_verifier: Option<Box<dyn SmartContractSignatureVerifier>>,
) -> Result<bool, ClientError>
where
    Client: XmtpBackendClient + Clone,

A static lookup method to verify if an identity is a member of an inbox