Where is ContainsKey() defined, is that a function you wrote?
if (PlayerDataMap.ContainsKey(Player)): { }
If you’re intending to check if the key exists, and do something if it doesn’t, I think it could be done something like this.
if:
aPlayer := PlayerDataMap[Player]
then:
# Do nothing (aPlayer was set successfully)
block:
else:
# The rest of your code to do something if there was no entry
There are probably other syntax/styles that accomplish the same thing in Verse (I’ve been using this style so far in my code).