from typing import Dict, List, TypeVar, Set, Generator
T = TypeVar( 'T' )

def dfs( graph: Dict[ T, List[ T ] ], initial: T ) \
        -> Generator[ T, None, None ]:
    seen : Set[ T ] = set()
    yield from dfs_rec( graph, initial, seen )

def dfs_rec( graph: Dict[ T, List[ T ] ], initial: T,
             seen: Set[ T ] ) -> Generator[ T, None, None ]:

    if initial in seen:
        return

    seen.add( initial )

    for n in graph[ initial ]:
        yield from dfs_rec( graph, n, seen )

    yield initial

import run_tests