Documentation for ResourceSerializer with includes is incorrect #1397

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• Problem/bug report.
• Feature request.
• Request for support. Note: Please try to avoid submitting issues for support requests. Use Gitter instead.

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• I've searched for an existing issue.
• I've asked my question on Gitter and have not received a satisfactory answer. NOTE - I tried to ask in Gitter but it sends me in an infinite redirect loop when I try to sign in.
• I've included a complete bug report template. This step helps us and allows us to see the bug without trying to reproduce the problem from your description. It helps you because you will frequently detect if it's a problem specific to your project. NOTE - I attempted to create a complete bug report, but I'm not sure how to use the template, and can't seem to find documentation about how it's supposed to be used and my best guess of running ruby rails_5_master.rb doesn't seem to work.
• The feature I'm asking for is compliant with the JSON:API spec.

Description

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Bug reports:

The documentation says that ResourceSerailizer should be able to include resources by doing something like this:

post = Post.find(1)

JSONAPI::ResourceSerializer.new(PostResource,
  include: ['comments'],
).serialize_to_hash(PostResource.new(post, nil))

But when I do this I don't get an included section in the serialized output.

Additionally I don't find any tests in the test suite that demonstrate the documented way of doing it, but I find several tests that seem to achieve includes via much more verbose and laborious methods.

Am I missing something?