MLHR-998 #comment adding type parameter for value in UniqueValueCount

I am adding type parameter for value in UniqueValueCount operator, this is needed because of previous operator is outputting something other than KeyValuePair<K, Object> then we get compilation error when we
try to connect output of upstream operator with input of UniqueValueCount, as type of KeyValuePair do not match,

other solution is to extend type parameter from object like  ? extends Object, I have chosen to add another type parameter for more compile time safety.