Variant data missing 'product_id' attribute when using pagination

[dom-dynamicos]

Issue summary

When retrieving all Variant records using pagination, the 'product_id' attribute is only returned for the first page of variants.

Expected behavior

I'm expecting 'product_id' to be present when calling 'shopify.Variant.find()' as well as after '.has_next_page()' has been called.

Actual behavior

Calling 'has_next_page()' seems to exclude 'product_id'. If attempting to access 'product_id' after 'has_next_page()' has been called, the following error is returned:
'File "[...]\Python\Python311\Lib\site-packages\pyactiveresource\activeresource.py", line ###, in getattr
raise AttributeError(name)
AttributeError: product_id'

Steps to reproduce the problem

1. variants = shopify.Variant.find()
2. for variant in variants:
   print(variant.product_id)
3. while variants.has_next_page():
   variants = variants.next_page()
   Run the same code as 2 again

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Checklist

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