fix: Correct Python code examples in inputs/outputs guide

[vdusek]

Note

Fixes and streamlines Python snippets in the inputs/outputs guide, correcting dataset push usage and formatting.

• Docs (inputs_outputs.md)
  • Python examples:
    • Correct dataset.push_items usage (push list; remove invalid key args) and adjust set_output({'solution': solution}).
    • Normalize imports and function definitions (is_on_apify, get_input, set_output, add_all_numbers), removing extra spaces and blank lines.
    • Minor cleanup for local I/O paths and JSON formatting in examples.

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[apify-service-account]

Preview for this PR was built for commit 5327aac and is ready at https://pr-2096.preview.docs.apify.com!

[honzajavorek]

The changes look okay to me. Is it worth indenting the JSON we're sending to the dataset? I don't know the internals enough to have an opinion.

Now about the elephant in the room. I know it probably wasn't the aim of this PR, but text on the whole page acts as if the Python Apify SDK didn't exist. Is it from times when it didn't exist? Because today it would be better to mention that in Python you'd use the SDK the same way as in Node.js, and have the example in a third language, e.g. PHP, Java, Go, you name it.

Even if your aim was just to fix errors in the code examples, I think it would be worth to fix sentences such as

If you are using Node.js for your repo's code, you can use the apify package. Otherwise, you can use the useful environment variables...

Alternatively, when writing in a language other than JavaScript, we can create our own...

etc., which completely ignore the existence of the Python SDK. What do you think?