Refactor pipe(as_tuples) into a separate method

[adrianeboyd]

Description

Refactor pipe(as_tuples) into a separate method

Types of change

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Checklist

• [x] I confirm that I have the right to submit this contribution under the project's MIT license.
• [x] I ran the tests, and all new and existing tests passed.
• [x] My changes don't require a change to the documentation, or if they do, I've added all required information.

[adrianeboyd]

The main advantage here is that the types are a lot simpler. Otherwise it's not really much benefit for the code or for users.

[adrianeboyd]

On second thought, we should implement this first in parallel in v3, raise a deprecation warning for as_tuples, and then remove it in v4.