Function im::lens::compose

pub fn compose<A, B, C, L, R>(left: &L, right: &R) -> Compose<A, B, C, L, R> where
    L: PartialLens<From = A, To = B>,
    R: PartialLens<From = B, To = C>, 

Compose a lens from A to B with a lens from B to C, yielding a lens from A to C.