[Feature Request]: Expose pvalue.Row in core.py rather than pvalue.py

What would you like to happen?

It's semantically confusing that Row is defined in pvalue.py. pvalues are abstract representations of data while Rows are actually concretely instantiated.

It might make more sense to put it in core.py? (with a lingering alias in pvalue.py for backwards compatibility)

Issue Priority

Priority: 2 (default / most feature requests should be filed as P2)

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