public String getCollectionType() {
	        return (sdFieldType == null)
                    ? "SINGLE"
                    : (sdFieldType instanceof WeightedSetDataType)
		                ? "WEIGHTEDSET"
                        : (sdFieldType instanceof ArrayDataType)
                            ? "ARRAY"
                            : "SINGLE";
	    }
Representation of an index field with name and data type.
config-model/src/main/java/com/yahoo/schema/derived/IndexSchema.java