def dfs(at1: Atom, m_append: Callable[[int], None]):
at1._visited = True # type: ignore[attr-defined]
m_append(at1.id)
for bond in at1.bonds:
at2 = bond.other_end(at1)
if not at2._visited: # type: ignore[attr-defined]
dfs(at2, m_append)
def dfs(at1: Atom, atom_set: Set[Atom]):
at1._visited = True
atom_set.add(at1)
for at2 in at1.neighbors():
if at2._visited:
continue
dfs(at2, atom_set)