Outdated pipelines SDK guide

[sarahmaddox]

The guide to creating a pipeline component instructs people to create a class that inherits from dsl.ContainerOp - class TrainerOp(dsl.ContainerOp)
https://www.kubeflow.org/docs/pipelines/sdk/build-component/#create-a-python-class-for-your-component

But the related sample has since been updated to use a function that returns a ContainerOp:
https://github.com/kubeflow/pipelines/blob/master/samples/xgboost-spark/xgboost-training-cm.py#L124

We should update the doc to match the sample.

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[OfficePop]

I'd like to contribute on this article next, @sarahmaddox if you could assign when you have a chance. Thanks!

[sarahmaddox]

Thanks @OfficePop

/assign @OfficePop

[OfficePop]

PR 971 created for this issue.

[sarahmaddox]

Congrats and thanks @OfficePop!

/close

[k8s-ci-robot]

@sarahmaddox: Closing this issue.

In response to this:

Congrats and thanks @OfficePop!

/close

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