(optional) If a default element is dropped, it can be passed here to help generation. Structure: unknown [type: Array, elementType: String] - The unslotted elements to be used for generated. measures [type: Array, elementType: String] - The measures (unique name) to be used for generation. rows [type: Array, elementType: String] - The rows (unique name) to be used for generation. columns [type: Array, elementType: String] - The columns (unique name) to be used for generation. slicers [type: Array, elementType: String] - The slicers (unique name) to be used for generation.