docs: include imports statements in examples code snippets

[shravanasati]

Changes proposed in this PR

I was browsing through the docs, and I copy pasted a code snippet from the examples section. It was missing an import statement included in the original example file but not in the docs. I've added all those missing line numbers in the examples.rst file.

It is very important to keep up to date tests and documentation.

• [ ] Tests added/updated
• [x] Documentation updated

Is your code right?

• [ ] PEP8 compliant
• [ ] flake8 passed

[BoboTiG]

Thank you @shravanasati 🥂