def traversierung_bfs(graph, start):
    """Returns the list of nodes in graph reachable from start, in breadth-first order."""
    sequence=[]  # list of nodes in breadth-first order
    candidates = [start]  # known nodes we should process
    
    while candidates:
        # Handle the next candidate:
        #  - remove from list
        #  - if not visited yet: add to sequence and add its neighbors
        node = candidates.pop(0)
        if node in sequence:
            continue
        sequence.append(node)
        for neighbor in graph[node]:
            candidates.append(neighbor)
    return sequence

print("bfs: ", traversierung_bfs(graph, "ksr"))