Some definitions of interest.
bchoose	Def @x:'a. p(x) == @x:'a. p(x)
	Thm* 'a:S, p:('a). (@x:'a. p(x))  'a
assert	Def b == if b True else False fi
	Thm* b:. b  Prop
label	Def t  ...$L == t
stype	Def S == {T:Type| x:T. True }
	Thm* S  Type{2}

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