diff --git a/api/dify_graph/graph/graph.py b/api/dify_graph/graph/graph.py
index 85117583e0..add69ad884 100644
--- a/api/dify_graph/graph/graph.py
+++ b/api/dify_graph/graph/graph.py
@@ -10,7 +10,6 @@ from pydantic import TypeAdapter
 from dify_graph.entities.graph_config import NodeConfigDict
 from dify_graph.enums import ErrorStrategy, NodeExecutionType, NodeState
 from dify_graph.nodes.base.node import Node
-from libs.typing import is_str
 
 from .edge import Edge
 from .validation import get_graph_validator
@@ -102,7 +101,7 @@ class Graph:
             source = edge_config.get("source")
             target = edge_config.get("target")
 
-            if not is_str(source) or not is_str(target):
+            if not isinstance(source, str) or not isinstance(target, str):
                 continue
 
             # Create edge
@@ -110,7 +109,7 @@ class Graph:
             edge_counter += 1
 
             source_handle = edge_config.get("sourceHandle", "source")
-            if not is_str(source_handle):
+            if not isinstance(source_handle, str):
                 continue
 
             edge = Edge(
diff --git a/api/libs/typing.py b/api/libs/typing.py
deleted file mode 100644
index f84e9911e0..0000000000
--- a/api/libs/typing.py
+++ /dev/null
@@ -1,9 +0,0 @@
-from typing import TypeGuard
-
-
-def is_str_dict(v: object) -> TypeGuard[dict[str, object]]:
-    return isinstance(v, dict)
-
-
-def is_str(v: object) -> TypeGuard[str]:
-    return isinstance(v, str)