graph1 = {'0':set(['1','2']),
         '1':set(['3','4']),
         '2':set(['5','6']),
         '3':set(['6']),
         '4':set(['7'])}

def bfs(graf, start, target):
    queue = [[start]]
    visited = set()
    i = 0
    while queue:
        i = i + 1
        path = queue.pop(0)
        state = path[-1]
        if state == target:
            print("Number of steps: ", i)
            return path
        elif state not in visited:
            for vertex in graf.get(state, []):
                if vertex not in visited:
                    path_new = list(path)
                    path_new.append(vertex)
                    queue.append(path_new)
            visited.add(state)
        lenght = len(queue)
        if lenght == 0:
            print("Not founded")
print("Results: ",bfs(graph1,'0','5'))