updated error message

[axiomcura]

Description

Thank you for your contribution to pycytominer!
Please succinctly summarize your proposed change.
What motivated you to make this change?

Summary

This PR addresses one of the reviewers’ comments:

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" When I used the function pycytominer.normalize() on a dataset originating from my own work, I encountered an error message saying

“No CP features found. Are you sure this dataframe is from CellProfiler?”.

I could easily fix the problem because I know the properties of a CellProfiler dataset, and the error message was hinting at some “Metadata_” missing.

The fix was very easy, I just needed to add the prefix “Metadata_” to my metadata columns. My dataset comes from another commonly used proprietary software called Harmony. I understand that the authors are in favor of using open-source resources, but I think that the pycytominer tool could be useful in a much larger context, and take as input different types of datasets. In the readme file, that I followed to perform the normalization, I couldn’t find anywhere that the dataset has to come from CellProfiler. ..."

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I replaced the ‘assert’ statement with an exception, as it’s considered bad practice to use assertions during runtime. Assertions can be disabled with the -o parameter, which means they aren’t reliable for handling errors in production code.
Here are some useful links:

• https://stackoverflow.com/questions/42837054/are-assert-methods-acceptable-in-production
• https://docs.astral.sh/ruff/rules/assert/
• https://stackoverflow.com/questions/1273211/disable-assertions-in-python

Additionally, I updated the error message to clarify that pycytominer infers CellProfiler features by default and provided guidance on how users can manually specify their feature space when working with non-CellProfiler data.

Please also link to any relevant issues that your code is associated with.

This code is also an addition to #430

What is the nature of your change?

• Bug fix (fixes an issue).
• Enhancement (adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).
• This change requires a documentation update.

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• New and existing unit tests pass locally with my changes.
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• I have deleted all non-relevant text in this pull request template.