Find the Town Judge - 10th May

Question - In a town, there are N people labelled from 1 to N.  There is a rumor that one of these people is secretly the town judge.
If the town judge exists, then:
1.	The town judge trusts nobody.
2.	Everybody (except for the town judge) trusts the town judge.
3.	There is exactly one person that satisfies properties 1 and 2.
You are given trust, an array of pairs trust[i] = [a, b] representing that the person labelled a trusts the person labelled b.
If the town judge exists and can be identified, return the label of the town judge.  Otherwise, return -1.

Solution 1 -  
def findJudge(self, N: int, trust: List[List[int]]) :
        trusted = dict.fromkeys(range(1,N+1), 0)
        for a,b in trust:
            trusted[a] -= 1
            trusted[b] += 1
        key = max(trusted, key=trusted.get)   # it will return the key for max value and max value will be possible only for jUDGE IF ITS EQUAL TO n-1
        return key if trusted[key]==N-1 else -1