public static ValueUpdate createMultiply(FieldValue key, Number factor) {
        return createMap(key, createMultiply(factor));
    }
Creates a new value update that multiplies a weight in a weighted set. Note that this method is just a convenience
method, it simply creates a multiply value update by calling createMultiply() and then creates a map value
update by calling createMap() with the key and the multiply value update as parameters.

@param key the key whose weight in the weighted set to multiply
@param factor the number to multiply by
@return a ValueUpdate specifying the multiplication
@see ValueUpdate#createMultiply(Number)
@see ValueUpdate#createMap(FieldValue, ValueUpdate)
document/src/main/java/com/yahoo/document/update/ValueUpdate.java