Function nested_loop_join 

pub fn nested_loop_join<L, R, O, P, OF>(
    left: &[L],
    right: &[R],
    predicate: P,
    output_fn: OF,
) -> Vec<O>
where
    P: Fn(&L, &R) -> bool,
    OF: Fn(&L, &R) -> O,

Performs a nested loop join using a predicate function.