Rearranged the existing code to make it more manageable.

src/gtfs/utils.rs

@@ -0,0 +1,27 @@
+use std::collections::HashSet;
+use crate::gtfs::structs::Gtfs;
+
+
+pub fn stop_ids_from_codes(gtfs: &Gtfs, stop_codes: &HashSet<String>) -> HashSet<String> {
+    let mut ids: HashSet<String> = HashSet::new();
+
+    for stop in &gtfs.stops {
+        let stop_number = stop.1.code.as_ref();
+        if stop_number.is_some() && stop_codes.contains(stop_number.unwrap().as_str()) {
+            ids.insert(stop.0.clone());
+        }
+    }
+    return ids;
+}
+
+pub fn route_ids_from_numbers(gtfs: &Gtfs, route_numbers: &HashSet<String>) -> HashSet<String> {
+    let mut ids: HashSet<String> = HashSet::new();
+
+    for route in &gtfs.routes {
+        let route_number = route.1.short_name.as_ref();
+        if route_number.is_some() && route_numbers.contains(route_number.unwrap().as_str()) {
+            ids.insert(route.0.clone());
+        }
+    }
+    return ids;
+}