$\forall$$A$:Type, $B$:($A$$\rightarrow$Type), ${\it eq}$:EqDecider($A$), $f_{1}$, $g$, $f_{2}$:$a$:$A$ fp$\rightarrow$ $B$($a$).
\\[0ex]$f_{1}$ $\subseteq$ $g$ $\Rightarrow$ $f_{2}$ $\subseteq$ $g$ $\Rightarrow$ $f_{1}$ $\oplus$ $f_{2}$ $\subseteq$ $g$