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$\vdash$  \=$\forall$$T$:Type, $l$:($T$ List), $x$, $y$, $z$:$T$.\+
\\[0ex]no\_repeats($T$;$l$) $\Rightarrow$ $x$ before $y$ $\in$ $l$ $\Rightarrow$ $y$ before $z$ $\in$ $l$ $\Rightarrow$ $x$ before $z$ $\in$ $l$
\-
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