Macro flat_take 

macro_rules! flat_take {
    ($i:expr, $len:expr, $f:ident) => { ... };
    ($i:expr, $len:expr, $submac:ident!( $($args:tt)*)) => { ... };
}

Available on (crate features rustls or boring or acme) and crate feature rustls only.

Combination and flat_map! and take! as first combinator