---

from collections import deque

vets = {"том", "джонни"}

def search(start):
    queue = deque(graph[start])
    searched = set()
    while queue:
        person = queue.popleft()
        if person not in searched:
            print("проверяем", person)
            if person in vets:
                return person
            queue += graph[person]
            searched.add(person)
    return None

print("нашли:", search("я"))