Custom schema issues / nested arrays

[dmsdd]

I'm trying to create a schema that will put a list of items from separate columns in to a nested array:

 "data": {
       "tags": ["cashier", "burger flipper", "fry cook"]
  }

Each item is in a different column in the source csv. I tried each column header as 'data_tags', but that only returns the first column with that header. I tried creating a custom schema, and setting the column headers to data_tags_1, data_tags_2,data_tags_3, but I don't think I understand how to use schema - I always get a KeyError on the first column of the csv.

Custom schema:
{"data": {"tags": ["data_tags_1", "data_tags_2", "data_tags_3"]}}

Any suggestions on how to accomplish a nested array?