Labels grouped by lines Document Understanding

Hello, we are trying to use Document Understanding using the KEY_VALUE_EXTRACTION method. The problem we are having is that in the demo within OCI itself, it scans invoices and groups the labels by lines, like in the next example (description, quantity, price…): 

However, when we try to label the data in a custom model as a key_value_extraction method, we do not have any method to categorize the label as an array/table. Does anyone know how to configure this so that it returns this in the lines section of an invoice? In our case, it concatenates all the fields in the same label without differentiating by line.