to_s: test
size: 20
to_json:
first: to_stest
product.metafields.custom["size"] =>
product.metafields.custom.size => 20

product.metafields.custom["first"] =>
product.metafields.custom.first => to_stest

product.metafields.custom["last"] =>
product.metafields.custom.last =>

product.metafields.custom["to_h"] => test
product.metafields.custom.to_h => test

product.metafields.custom["to_liquid"] =>
product.metafields.custom.to_liquid =>