diff --git a/src/daglib/dag.py b/src/daglib/dag.py
index 0227808..e3d7b72 100644
--- a/src/daglib/dag.py
+++ b/src/daglib/dag.py
@@ -11,6 +11,7 @@ type dictset = defaultdict[T, set[T]]
 
 T = TypeVar("T")
 
+
 @dataclass(repr=False)
 class DAG(Generic[T], MutableMapping[T, DAGSetView[T]]):
     """
@@ -53,22 +54,25 @@ class DAG(Generic[T], MutableMapping[T, DAGSetView[T]]):
         dagset.on_remove = _on_remove
         return dagset
 
-    def __setitem__(self, u: T, vs: Iterable[T]) -> None:
-        match vs:
-            case set():
-                self._succ[u] |= vs
-                for v in vs:
-                    self._pred[v] |= {u}
-            case str():
-                self._succ[u] |= {vs}
-                self._pred[vs] |= {u}
-            case Iterable():
-                self._succ[u] |= set(vs)
-                for v in vs:
-                    self._pred[v] |= {u}
-            case _:
-                self._succ[u] |= {vs}
-                self._pred[vs] |= {u}
+    def __setitem__(self, u: T, value: Iterable[T]) -> None:
+        match value:
+            case set() as vs:
+                self.__setmultiple__(u, vs)
+            case str() as v:
+                self.__setsingle__(u, v)
+            case Iterable() as vs:
+                self.__setmultiple__(u, vs)
+            case _ as v:
+                self.__setsingle__(u, v)
+
+    def __setsingle__(self, u: T, v: T) -> None:
+        self._succ[u] |= {v}
+        self._pred[v] |= {u}
+
+    def __setmultiple__(self, u: T, vs: Iterable[T]) -> None:
+        self._succ[u] |= set(vs)
+        for v in vs:
+            self._pred[v] |= {u}
 
     def __delitem__(self, u: T) -> None:
         self.discard_node(u)