support custom weight loader for model runner (#7122)

Co-authored-by: kavioyu <kavioyu@tencent.com>

python/sglang/srt/utils.py

@@ -2340,3 +2340,16 @@ class LazyValue:
             self._value = self._creator()
             self._creator = None
         return self._value
+
+
+def dynamic_import(func_path: str):
+    parts = func_path.split(".")
+    if len(parts) < 2:
+        raise ValueError(
+            "func_path should contain both module name and func name (such as 'module.func')"
+        )
+    module_path = ".".join(parts[:-1])
+    func_name = parts[-1]
+    module = importlib.import_module(module_path)
+    func = getattr(module, func_name)
+    return func