fix docs and tests

Signed-off-by: aiordache <anca.iordache@docker.com>

docker/models/images.py

@@ -399,8 +399,7 @@ def pull(self, repository, tag='latest', **kwargs):
         """
         Pull an image of the given name and return it. Similar to the
         ``docker pull`` command.
-        If no tag is specified, all tags from that repository will be
-        pulled.
+        If tag is None, all tags from that repository will be pulled.
 
         If you want to get the raw pull output, use the
         :py:meth:`~docker.api.image.ImageApiMixin.pull` method in the
@@ -416,7 +415,7 @@ def pull(self, repository, tag='latest', **kwargs):
 
         Returns:
             (:py:class:`Image` or list): The image that has been pulled.
-                If no ``tag`` was specified, the method will return a list
+                If ``tag`` is None, the method will return a list
                 of :py:class:`Image` objects belonging to this repository.
 
         Raises:

tests/unit/models_containers_test.py

@@ -233,7 +233,7 @@ def test_run_pull(self):
 
         assert container.id == FAKE_CONTAINER_ID
         client.api.pull.assert_called_with(
-            'alpine', platform=None, tag=None, stream=True
+            'alpine', platform=None, tag='latest', stream=True
         )
 
     def test_run_with_error(self):

tests/unit/models_images_test.py

@@ -54,7 +54,7 @@ def test_pull(self):
 
     def test_pull_multiple(self):
         client = make_fake_client()
-        images = client.images.pull('test_image')
+        images = client.images.pull('test_image', tag=None)
         client.api.pull.assert_called_with(
             'test_image', tag=None, stream=True
         )