make some types optional to avoid needing to typecast

schema.graphql

@@ -6,11 +6,11 @@ type Query {
 type System {
   id: ID!
   name: String!
-  routes: [Route!]!
+  routes: [Route!]
   route(id: ID): Route
-  stops: [Stop!]!
+  stops: [Stop!]
   stop(id: ID): Stop
-  shuttles: [Shuttle!]!
+  shuttles: [Shuttle!]
   shuttle(id: ID): Shuttle
 }
 
@@ -18,9 +18,9 @@ type Route {
   name: String!
   id: ID!
   system: System!
-  orderedStops: [OrderedStop!]!
+  orderedStops: [OrderedStop!]
   nextOrderedStop(forStopId: ID): OrderedStop
-  shuttles: [Shuttle!]!
+  shuttles: [Shuttle!]
   polylineCoordinates: [Coordinates!]!
   color: String!
 }
@@ -37,8 +37,8 @@ type Stop {
   name: String!
   coordinates: Coordinates!
   system: System!
-  etas: [ETA!]!
-  orderedStops: [OrderedStop!]!
+  etas: [ETA!]
+  orderedStops: [OrderedStop!]
 }
 
 type Coordinates {
@@ -56,8 +56,8 @@ type Shuttle {
   name: String!
   id: ID!,
   coordinates: Coordinates!
-  route: Route!
-  system: System!
-  etas: [ETA!]!
+  route: Route
+  system: System
+  etas: [ETA!]
   eta(forStopId: ID): ETA
 }