Def MostPopularKey (d, default) :
"" "Given a dict, return the key corresponding to the largest
Value. Returns' default 'if the dict is empty. "" "
X=[(n, k) for (k, v) in d.i teritems ()]
If not x: return default
X.s ort ()
Return the x [1] [1]

I ask x=[(n, k) for (k, v) in d.i teritems ()]
What is the meaning of this sentence?