`client.containers.run()` doesn't exist

Hi there,

Today I decided to look into docker-py for a project I will be working on in the coming months. After a fresh install of docker and docker-py today, I must say that, somehow, docker-py doesn't quite work.
The getting started examples show this code:

>>> import docker
>>> client = docker.from_env()
>>> client.containers.run("ubuntu", "echo hello world")
'hello world\n'

But when I run this, I see

In [1]: import docker                                                                                                                                                                                                                         
In [2]: client = docker.from_env()                                                                                                                                                                                                            
In [3]: client.containers.run("ubuntu", "echo hello world")                                                                                                                                                                                                         
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-3-5336699d83c5> in <module>
----> 1 client.containers.run()

AttributeError: 'function' object has no attribute 'run'

I also tried to manually create an instance of the docker.Client as detailed in the docs

In [1]: import docker                                                                                                                                                                                                                         
# Note: The following line from the docs fails to execute... :-(
In [2]: client = docker.DockerClient(base_url='unix://var/run/docker.sock')                                                                                                                                                                   
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-2-a0131c4bce50> in <module>
----> 1 client = docker.DockerClient(base_url='unix://var/run/docker.sock')

AttributeError: module 'docker' has no attribute 'DockerClient'

In [3]: client = docker.Client(base_url='unix://var/run/docker.sock')                                                                                                                                                                         
In [4]: client.containers.run("hello-world")                                                                                                                                                                                                  
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-4-a00eac6bdc71> in <module>
----> 1 client.containers.run("hello-world")

AttributeError: 'function' object has no attribute 'run'

Calling docker through the CLI works as expected

$ docker run hello-world

Hello from Docker!
This message shows that your installation appears to be working correctly.
[ ... ]

Note that I am a member of the docker group on my system. I already tried to reboot my system but to no avail.

Here's some info on my system:

$ docker --version
Docker version 19.03.11, build 42e35e61f3

$ pip3 show docker
Name: docker
Version: 4.2.1
Summary: A Python library for the Docker Engine API.
Home-page: https://github.com/docker/docker-py
Author: None
Author-email: None
License: Apache License 2.0
Location: /home/<user>/.local/lib/python3.7/site-packages
Requires: websocket-client, six, requests
Required-by: 

$ cat /etc/os-release 
PRETTY_NAME="Debian GNU/Linux 10 (buster)"
NAME="Debian GNU/Linux"
VERSION_ID="10"
VERSION="10 (buster)"
VERSION_CODENAME=buster

I'd be grateful for any help and/or pointers to a possible cause...

Start with the getting-started example using docker.from_env() and client.containers.run(), then compare it with the client reference and the reported docker 4.2.1 installation. Reproduce the AttributeError and determine whether the library behavior or the linked documentation is inconsistent; done means the documented client usage works or the documentation accurately reflects the supported API.