$\forall$$A$:Type, $d_{1}$, $d_{2}$, $d_{3}$, $d_{4}$:EqDecider($A$), $B$:($A$$\rightarrow$Type), $f$, $g$:$a$:$A$ fp$\rightarrow$ $B$($a$), $x$:$A$, $z$:$B$($x$).
\\[0ex]$f$ $\subseteq$ $g$ $\Rightarrow$ $x$ $\in$ dom($f$) $\Rightarrow$ $f$($x$)?$z$ $=$ $g$($x$)?$z$ $\in$ $B$($x$)