You are given the following MapSet wrapper arround Dafny's maps, which

fixes the type of the "values" to be booleans. As a result,

one can think of a MapSet as a set, where an element is considered

to be in the MapSet iff it maps to true in the wrapped map.

Implement the following set API calls in terms of this

wrapper, by invoking Dafny map functions as seen on the slides.

$*/$

datatype MapSet $=$ MapSet $($s : map$)$

predicate member $($m:MapSet, x:T$)\{$

$//$ Replace with your definition

true

$\}$

function size $($m:MapSet$)$: int $\{$

$//$ Replace with your definition

$42$

$\}$

function insert $($m:MapSet, x:T$)$: MapSet $\{$

$//$ Replace with your definition

MapSet $($map$[])$

$\}$

function delete $($m:MapSet, x:T$)$: MapSet $\{$

$//$ Replace with your definition

MapSet $($map$[])$

$\}$