In the variable setup you have
LET chemical_formula_as_mathml be the result of calling [check for node](https://github.com/w3c/publ-a11y/issues/new#check-for-node) on onix, /ONIXMessage/Product/DescriptiveDetail/ProductFormFeature[ProductFormFeatureType = "09" and ProductFormFeatureValue = "34"].
In the variable setup you have
LET chemical_formula_as_mathml be the result of calling [check for node](https://github.com/w3c/publ-a11y/issues/new#check-for-node) on onix, /ONIXMessage/Product/DescriptiveDetail/ProductFormFeature[ProductFormFeatureType = "09" and ProductFormFeatureValue = "34"].But this is not defined in the section above.