Method Kiboko\Contract\Pipeline\FlushableInterface::flush() has invalid return type Kiboko\Component\Bucket\EmptyResultBucket.

Method Kiboko\Contract\Pipeline\FlushableInterface::flush() return type with generic interface Kiboko\Contract\Bucket\ResultBucketInterface does not specify its types: Type

PHPDoc tag @return with type Kiboko\Component\Bucket\EmptyResultBucket|Kiboko\Contract\Bucket\ResultBucketInterface<Type> is not subtype of native type Kiboko\Contract\Bucket\ResultBucketInterface.