Function actix_web::web::md

pub fn md<F, R, S, P, B>(
    f: F
) -> impl Transform<S, Request = ServiceRequest<P>, Response = ServiceResponse<B>, Error = Error, InitError = ()> where
    S: Service<Request = ServiceRequest<P>, Response = ServiceResponse<B>, Error = Error>,
    F: FnMut(ServiceRequest<P>, &mut S) -> R + Clone,
    R: IntoFuture<Item = ServiceResponse<B>, Error = Error>, 

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