Services Documentation Error

Problem:

Apparently the return type in the documentation does not match the actual type that is returned when using Service.scale() method. If you look at here it is stated that it will return a bool. However, when you actually call the function it will return a dictionary. I don't know what this dictionary relates to otherwise I'd be glad to fix it myself and make pull-request. Thanks for your awesome support!

How to replicate:

steps:

1. Create a sample service like a Redis service: docker service create --name redis-service redis
2. Run python (make sure you have installed docker SDK before)
3. Follow the process below:

import docker
client = docker.client.from_env()
service = client.services.get("redis-service")
res = service.scale(3)
print(res)
### This is what you'll get: {'Warning': None}
### but in the documentation it is stated that it will return a boolean value

Here are my environment specs when I tested this:

Environment:

• Docker SDK Version: 4.2.0
• DockerDaemon Version: 18.09.07
• OS: Ubuntu Server 18.04 LTS

Start with docker/models/services.py at the documented Service.scale() method and reproduce the issue using the supplied Docker service and Python example. Compare the documented return type with the observed {'Warning': None} result and trace what that response represents. Done means the documentation accurately describes the returned value and its meaning.