public static FieldUpdate createDivide(Field field, FieldValue key, Number divisor) {
        return new FieldUpdate(field, ValueUpdate.createDivide(key, divisor));
    }
Creates a new field update, with one encapsulated value update that divides a weight in a weighted set.

@param field     the field to divide one of the weights of
@param key the key whose weight in the weighted set to divide
@param divisor the number to divide by
@return a FieldUpdate specifying the division
@throws IllegalArgumentException if key is not equal to the nested type of the weighted set
@see ValueUpdate#createDivide(Number)
@see ValueUpdate#createMap(FieldValue, ValueUpdate)
document/src/main/java/com/yahoo/document/update/FieldUpdate.java