From type/QuantHash

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method Setty(--> Setty:D)

Coerce the QuantHash object to the equivalent object that uses the Setty role. Note that for Mixy type coercion items with negative values will be skipped.

my %b is Bag = one => 1, two => 2;
say %b.Setty; # OUTPUT: «Set(one two)␤» 
my %m is Mix = one => 1, minus => -1;
say %m.Setty; # OUTPUT: «Set(one)␤»