Function handle_vid_disperse_request 

fn handle_vid_disperse_request<T, S>(
    epoch_membership_coordinator: EpochMembershipCoordinator<T>,
    send: S,
    public_key: T::SignatureKey,
    private_key: <T::SignatureKey as SignatureKey>::PrivateKey,
    vid_disperse_request: VidDisperseRequest<T>,
    tracer: Option<LeaderTracerHandle>,
    built: Option<BuiltDispersal<T>>,
) -> Result<VidDisperseOutput, VidDisperseError>
where
    T: NodeType,
    S: Fn(&T::SignatureKey, &Message<T, Validated>) -> Result<(), NetworkError> + Clone + Send,