feat: extract model runtime

Signed-off-by: -LAN- <laipz8200@outlook.com>

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(