In our program based on Flink 1.7.2, we used method ConfigOption#hasDeprecatedKeys. But, this method was renamed to hasFallbackKeys in
FLINK-10436. So after we bump our flink version to 1.9.0, we meet compile error.
It seems we replaced the deprecated key with an entity FallbackKey. However, I still see the method withDeprecatedKeys. Since we keep the method withDeprecatedKeys, why not keep the method hasDeprecatedKeys. Although, this public API did not marked as Public annotation. IMHO, ConfigOption is hosted in flink-core module, many users also use it, we should maintain the compatibility as far as possible.