Get Record but instead of the id, it is the id from a list.

I have a list of vendors that may belong to one or multiple categories. What I am trying to do is get the vendors based on their categories.

For now, I am able to get the categories, store them in an array, I am having issues when trying to do a for each loop to get the vendor based on the array of categories. Please see my function stack below

I am receiving an error on the 4th function, it is

message:

ParseError: Invalid value for param:dbo.category

tried changing it to category.category since it is a list and the new error message is

message:

Unsupported parameter reference - xdo.category.category

Any help would be appreciated since I am not sure if what I am thinking of is possible.

Thank you