Type parameter 'T' has nullable upper bound, so override has incorrect signature comparing with a base member with NotNull annotation. Please add a non-nullable upper bound (e.g. Any) to the type parameter. See https://kotlinlang.org/docs/generics.html#upper-bounds and https://youtrack.jetbrains.com/issue/KT-36770 for more details. This warning will become an error soon. Signed-off-by: Aayush Gupta <aayushgupta219@gmail.com>