Support `not in` contains expressions
I greatly appreciate the readability of the syntactic sugar of in
expressions, but it loses a lot of that readability when testing for the negation.
E.g I find foo in bar
more readable than bar.contains(foo)
, but I find !(foo in bar)
less readable than !bar.contains(foo)
.
So it would be good to have some sugar for not-in expressions. I'd suggest again using Python's not in
, but even something like not-in
would be an improvement.