Function gluon_base::merge::merge3

pub fn merge3<F, A: ?Sized, B: ?Sized, C: ?Sized, R>(
    a_original: &A, 
    a: Option<A::Owned>, 
    b_original: &B, 
    b: Option<B::Owned>, 
    c_original: &C, 
    c: Option<C::Owned>, 
    f: F
) -> Option<R> where
    A: ToOwned,
    B: ToOwned,
    C: ToOwned,
    F: FnOnce(A::Owned, B::Owned, C::Owned) -> R,