Update dataloader docs

Author: jkimbo

docs/execution/dataloader.rst

@@ -4,7 +4,7 @@ Dataloader
 DataLoader is a generic utility to be used as part of your application's
 data fetching layer to provide a simplified and consistent API over
 various remote data sources such as databases or web services via batching
-and caching.
+and caching. It is provided by a seperate package `aiodataloader <https://pypi.org/project/aiodataloader/>`.
 
 
 Batching
@@ -15,32 +15,31 @@ Create loaders by providing a batch loading function.
 
 .. code:: python
 
-    from promise import Promise
-    from promise.dataloader import DataLoader
+    from aiodataloader import DataLoader
 
     class UserLoader(DataLoader):
-        def batch_load_fn(self, keys):
-            # Here we return a promise that will result on the
-            # corresponding user for each key in keys
-            return Promise.resolve([get_user(id=key) for key in keys])
+        async def batch_load_fn(self, keys):
+            # Here we call a function to return a user for each key in keys
+            return [get_user(id=key) for key in keys]
 
 
-A batch loading function accepts a list of keys, and returns a ``Promise``
-which resolves to a list of ``values``.
+A batch loading async function accepts a list of keys, and returns a list of ``values``.
 
 Then load individual values from the loader. ``DataLoader`` will coalesce all
 individual loads which occur within a single frame of execution (executed once
-the wrapping promise is resolved) and then call your batch function with all
+the wrapping event loop is resolved) and then call your batch function with all
 requested keys.
 
 
 .. code:: python
 
     user_loader = UserLoader()
 
-    user_loader.load(1).then(lambda user: user_loader.load(user.best_friend_id))
+    user1 = await user_loader.load(1)
+    user1_best_friend = await user_loader.load(user1.best_friend_id))
 
-    user_loader.load(2).then(lambda user: user_loader.load(user.best_friend_id))
+    user2 = await user_loader.load(2)
+    user2_best_friend = await user_loader.load(user2.best_friend_id))
 
 
 A naive application may have issued *four* round-trips to a backend for the
@@ -54,9 +53,9 @@ make sure that you then order the query result for the results to match the keys
 .. code:: python
 
    class UserLoader(DataLoader):
-       def batch_load_fn(self, keys):
+       async def batch_load_fn(self, keys):
            users = {user.id: user for user in User.objects.filter(id__in=keys)}
-           return Promise.resolve([users.get(user_id) for user_id in keys])
+           return [users.get(user_id) for user_id in keys]
 
 
 ``DataLoader`` allows you to decouple unrelated parts of your application without
@@ -111,8 +110,8 @@ leaner code and at most 4 database requests, and possibly fewer if there are cac
         best_friend = graphene.Field(lambda: User)
         friends = graphene.List(lambda: User)
 
-        def resolve_best_friend(root, info):
-            return user_loader.load(root.best_friend_id)
+        async def resolve_best_friend(root, info):
+            return await user_loader.load(root.best_friend_id)
 
-        def resolve_friends(root, info):
-            return user_loader.load_many(root.friend_ids)
+        async def resolve_friends(root, info):
+            return await user_loader.load_many(root.friend_ids)