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

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