Added starwars relay example

docs/playground/examples/starwars_relay.graphql

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+query {
+  empire {
+    id
+    name
+    ships(first:2) {
+      edges {
+        node {
+          id
+          name
+        }
+      }
+    }
+  }
+  node(id:"U2hpcDo4") {
+    id
+    ... on Ship {
+      name
+    }
+  }
+}

docs/playground/examples/starwars_relay.schema.py

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+import graphene
+from graphene import relay, resolve_only_args
+
+class Ship(relay.Node):
+    '''A ship in the Star Wars saga'''
+    name = graphene.String(description='The name of the ship.')
+
+    @classmethod
+    def get_node(cls, id, info):
+        return get_ship(id)
+
+class Faction(relay.Node):
+    '''A faction in the Star Wars saga'''
+    name = graphene.String(description='The name of the faction.')
+    ships = relay.ConnectionField(
+        Ship, description='The ships used by the faction.')
+
+    @resolve_only_args
+    def resolve_ships(self, **args):
+        # Transform the instance ship_ids into real instances
+        return [get_ship(ship_id) for ship_id in self.ships]
+
+    @classmethod
+    def get_node(cls, id, info):
+        return get_faction(id)
+
+class IntroduceShip(relay.ClientIDMutation):
+    class Input:
+        ship_name = graphene.String(required=True)
+        faction_id = graphene.String(required=True)
+
+    ship = graphene.Field(Ship)
+    faction = graphene.Field(Faction)
+
+    @classmethod
+    def mutate_and_get_payload(cls, input, info):
+        ship_name = input.get('ship_name')
+        faction_id = input.get('faction_id')
+        ship = create_ship(ship_name, faction_id)
+        faction = get_faction(faction_id)
+        return IntroduceShip(ship=ship, faction=faction)
+
+
+class Query(graphene.ObjectType):
+    rebels = graphene.Field(Faction)
+    empire = graphene.Field(Faction)
+    node = relay.NodeField()
+
+    @resolve_only_args
+    def resolve_rebels(self):
+        return get_rebels()
+
+    @resolve_only_args
+    def resolve_empire(self):
+        return get_empire()
+
+
+class Mutation(graphene.ObjectType):
+    introduce_ship = graphene.Field(IntroduceShip)
+
+schema = graphene.Schema(name='Starwars Relay Schema')
+schema.query = Query
+schema.mutation = Mutation
+
+xwing = Ship(
+    id='1',
+    name='X-Wing',
+)
+ywing = Ship(
+    id='2',
+    name='Y-Wing',
+)
+awing = Ship(
+    id='3',
+    name='A-Wing',
+)
+
+# Yeah, technically it's Corellian. But it flew in the service of the rebels,
+# so for the purposes of this demo it's a rebel ship.
+falcon = Ship(
+    id='4',
+    name='Millenium Falcon',
+)
+homeOne = Ship(
+    id='5',
+    name='Home One',
+)
+tieFighter = Ship(
+    id='6',
+    name='TIE Fighter',
+)
+tieInterceptor = Ship(
+    id='7',
+    name='TIE Interceptor',
+)
+executor = Ship(
+    id='8',
+    name='Executor',
+)
+rebels = Faction(
+    id='1',
+    name='Alliance to Restore the Republic',
+    ships=['1', '2', '3', '4', '5']
+)
+empire = Faction(
+    id='2',
+    name='Galactic Empire',
+    ships=['6', '7', '8']
+)
+data = {
+    'Faction': {
+        '1': rebels,
+        '2': empire
+    },
+    'Ship': {
+        '1': xwing,
+        '2': ywing,
+        '3': awing,
+        '4': falcon,
+        '5': homeOne,
+        '6': tieFighter,
+        '7': tieInterceptor,
+        '8': executor
+    }
+}
+
+def create_ship(ship_name, faction_id):
+    from .schema import Ship
+    next_ship = len(data['Ship'].keys()) + 1
+    new_ship = Ship(
+        id=str(next_ship),
+        name=ship_name
+    )
+    data['Ship'][new_ship.id] = new_ship
+    data['Faction'][faction_id].ships.append(new_ship.id)
+    return new_ship
+
+def get_ship(_id):
+    return data['Ship'][_id]
+
+def get_faction(_id):
+    return data['Faction'][_id]
+
+def get_rebels():
+    return get_faction('1')
+
+def get_empire():
+    return get_faction('2')