public static FieldUpdate createMultiply(Field field, Number factor) {
        return new FieldUpdate(field, ValueUpdate.createMultiply(factor));
    }
Creates a new field update, with one encapsulated value update that multiplies a value.
Note that the data type must be a numeric type.

@param field     the field to multiply the value of
@param factor the number to multiply by
@return a FieldUpdate specifying the multiplication
@throws UnsupportedOperationException if the data type is non-numeric
@see ValueUpdate#createMultiply(Number)
document/src/main/java/com/yahoo/document/update/FieldUpdate.java