Find the Town Judge

from collections import defaultdict

class Solution:
    def findJudge(self, N: int, trust: List[List[int]]) -> int:
        # If N is 1 and there are no relationships, return 1
        if N == 1 and len(trust) == 0:
            return 1

        # Create 2 dictionaries inbound and outbound
        inbound = defaultdict(int)
        outbound = defaultdict(int)

        # Iterate through trust array
        for relationship in trust:
            # Extract a_i and b_i
            a_i = relationship[0]
            b_i = relationship[1]
            # Increment a_i in outbound dict
            outbound[a_i] += 1
            # Increment b_i in inbound dict
            inbound[b_i] += 1

        # Iterate through inbound dict:
        for k, v in inbound.items():
            # If N-1 in inbound value for key k
            if v == N-1:
                # If the value for key k is 0 in outbound
                if outbound[k] == 0:
                    # Return town judge if any.
                    # Not possible to have 2 nodes that both satisfy town judge requirements.
                    return k

        # If no town judge, return -1
        return -1