diff --git a/mongoengine/document.py b/mongoengine/document.py
index ae5f585d..2e3eee9d 100644
--- a/mongoengine/document.py
+++ b/mongoengine/document.py
@@ -166,7 +166,7 @@ class Document(BaseDocument):
     @classmethod
     def _get_collection(cls):
         """Returns the collection for the document."""
-        #TODO: use new get_collection() with PyMongo3 ?
+        # TODO: use new get_collection() with PyMongo3 ?
         if not hasattr(cls, '_collection') or cls._collection is None:
             db = cls._get_db()
             collection_name = cls._get_collection_name()
@@ -308,7 +308,9 @@ class Document(BaseDocument):
                     object_id = collection.insert(doc, **write_concern)
                 else:
                     object_id = collection.save(doc, **write_concern)
-                    # Pymongo 3.0 bug, fix scheduled for 3.0.1
+                    # TODO: Pymongo 3.0 bug, fix scheduled for 3.0.1
+                    # In PyMongo 3.0, the save() call calls internally the _update() call
+                    # but they forget to return the _id value passed back, therefore getting it back here
                     if not object_id and pymongo.version_tuple == (3, 0):
                         object_id = self._qs.filter(**self._object_key).first() and \
                                     self._qs.filter(**self._object_key).first().pk
diff --git a/mongoengine/queryset/base.py b/mongoengine/queryset/base.py
index 2e087e10..803374bd 100644
--- a/mongoengine/queryset/base.py
+++ b/mongoengine/queryset/base.py
@@ -930,6 +930,7 @@ class BaseQuerySet(object):
             plan = pprint.pformat(plan)
         return plan
 
+    # DEPRECATED. Has no more impact on PyMongo 3+
     def snapshot(self, enabled):
         """Enable or disable snapshot mode when querying.
 
@@ -1419,7 +1420,8 @@ class BaseQuerySet(object):
                 cursor_args['slave_okay'] = self._slave_okay
         else:
             fields_name = 'projection'
-            # snapshot seems not to be handled at all by PyMongo 3+
+            # snapshot is not to handled at all by PyMongo 3+
+            # TODO: raise a warning?
             cursor_args = {
                 'no_cursor_timeout': self._timeout
             }
diff --git a/tests/fields/fields.py b/tests/fields/fields.py
index 3b860cc7..0dc239c4 100644
--- a/tests/fields/fields.py
+++ b/tests/fields/fields.py
@@ -2491,7 +2491,8 @@ class FieldTest(unittest.TestCase):
         binary_id = uuid.uuid4().bytes
         att = Attachment(id=binary_id).save()
         self.assertEqual(1, Attachment.objects.count())
-        self.assertNotEqual(None, Attachment.objects.filter(id=binary_id).first())
+        # TODO use assertIsNotNone once Python 2.6 support is dropped
+        self.assertFalse(Attachment.objects.filter(id=binary_id).first() is not None)
         att.delete()
         self.assertEqual(0, Attachment.objects.count())