I want to check if a key is in a set, and pop! it if it is the case.
1. In order to do that, I can rely on a try / catch statement (i.e. try pop!(x, key)) or a default key (i.e. pop!(x, key, nothing)). Is one preferable to the other in term of speed? 2.. pop!(x, key, nothing) returns nothing even if key is in x. Is this expected? nothing == pop!(Set(1:2), 2, nothing) true
