No Output Requested while materializer should lead to error

[swapdewalkar]

Address #796

Changes

Added a check to to throw Error if materializer are 0.
Added Test case for the same

How I tested this

Unit Tested
Run Example on local as well

Notes

Checklist

• PR has an informative and human-readable title (this will be pulled into the release notes)
• Changes are limited to a single goal (no scope creep)
• Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future TODOs are captured in comments
• Project documentation has been updated if adding/changing functionality.

[skrawcz]

This should still work because processed_data was requested as additional vars. So this means the check in the code isn't in the right place or needs another clause.

But this should fail as there is nothing requested to be computed:

        dr.materialize(
            from_.json(target="input_data", path=value(path_in)),
            inputs={"output_path": str(path_out)},
        )

So good to have both cases to test.

[skrawcz]

LGTM