diff --git a/python/nn4k/invoker/base.py b/python/nn4k/invoker/base.py
index 617fae27..62087782 100644
--- a/python/nn4k/invoker/base.py
+++ b/python/nn4k/invoker/base.py
@@ -1,4 +1,3 @@
-# coding: utf-8
 # Copyright 2023 Ant Group CO., Ltd.
 #
 # Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
@@ -10,8 +9,6 @@
 # is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 # or implied.
 
-# Copyright (c) Antfin, Inc. All rights reserved.
-import json
 import os
 from abc import ABC
 from typing import Union
@@ -85,13 +82,9 @@ class LLMInvoker(NNInvoker):
 
     @classmethod
     def from_config(cls, nn_config: Union[str, dict]):
-        try:
-            if isinstance(nn_config, str):
-                with open(nn_config, "r") as f:
-                    nn_config = json.load(f)
-        except:
-            raise ValueError("cannot decode config file")
+        from nn4k.utils.config_parsing import preprocess_config
 
+        nn_config = preprocess_config(nn_config)
         if nn_config.get("invoker_type", "LLM") == "LLM":
 
             o = cls.__new__(cls)
diff --git a/python/nn4k/invoker/openai_invoker.py b/python/nn4k/invoker/openai_invoker.py
index b5a422b0..034da765 100644
--- a/python/nn4k/invoker/openai_invoker.py
+++ b/python/nn4k/invoker/openai_invoker.py
@@ -9,70 +9,27 @@
 # is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 # or implied.
 
-from typing import Any
 from typing import Union
 
 from nn4k.invoker import NNInvoker
 
 
 class OpenAIInvoker(NNInvoker):
-    @classmethod
-    def _preprocess_config(cls, nn_config: Union[str, dict]) -> dict:
-        try:
-            if isinstance(nn_config, str):
-                with open(nn_config, "r") as f:
-                    nn_config = json.load(f)
-        except:
-            raise ValueError("cannot decode config file")
-        return nn_config
-
-    @classmethod
-    def _get_field(cls, nn_config: dict, name: str, text: str) -> Any:
-        value = nn_config.get(name)
-        if value is None:
-            message = "%s %r not found" % (text, name)
-            raise ValueError(message)
-        return value
-
-    @classmethod
-    def _get_string_field(cls, nn_config: dict, name: str, text: str) -> str:
-        value = cls._get_field(nn_config, name, text)
-        if not isinstance(value, str):
-            message = "%s %r must be string; " % (text, name)
-            message += "%r is invalid" % (value,)
-            raise TypeError(message)
-        return value
-
-    @classmethod
-    def _get_int_field(cls, nn_config: dict, name: str, text: str) -> int:
-        value = cls._get_field(nn_config, name, text)
-        if not isinstance(value, int):
-            message = "%s %r must be integer; " % (text, name)
-            message += "%r is invalid" % (value,)
-            raise TypeError(message)
-        return value
-
-    @classmethod
-    def _get_positive_int_field(cls, nn_config: dict, name: str, text: str) -> int:
-        value = cls._get_int_field(nn_config, name, text)
-        if value <= 0:
-            message = "%s %r must be positive integer; " % (text, name)
-            message += "%r is invalid" % (value,)
-            raise ValueError(message)
-        return value
-
     @classmethod
     def _parse_config(cls, nn_config: dict) -> dict:
-        openai_api_key = cls._get_string_field(
+        from nn4k.utils.config_parsing import get_string_field
+        from nn4k.utils.config_parsing import get_positive_int_field
+
+        openai_api_key = get_string_field(
             nn_config, "openai_api_key", "openai api key"
         )
-        openai_api_base = cls._get_string_field(
+        openai_api_base = get_string_field(
             nn_config, "openai_api_base", "openai api base"
         )
-        openai_model_name = cls._get_string_field(
+        openai_model_name = get_string_field(
             nn_config, "openai_model_name", "openai model name"
         )
-        openai_max_tokens = cls._get_positive_int_field(
+        openai_max_tokens = get_positive_int_field(
             nn_config, "openai_max_tokens", "openai max tokens"
         )
         config = dict(
@@ -86,8 +43,9 @@ class OpenAIInvoker(NNInvoker):
     @classmethod
     def from_config(cls, nn_config: Union[str, dict]):
         import openai
+        from nn4k.utils.config_parsing import preprocess_config
 
-        nn_config = cls._preprocess_config(nn_config)
+        nn_config = preprocess_config(nn_config)
         config = cls._parse_config(nn_config)
 
         o = cls.__new__(cls)
diff --git a/python/nn4k/utils/__init__.py b/python/nn4k/utils/__init__.py
new file mode 100644
index 00000000..19913efa
--- /dev/null
+++ b/python/nn4k/utils/__init__.py
@@ -0,0 +1,10 @@
+# Copyright 2023 Ant Group CO., Ltd.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+# in compliance with the License. You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software distributed under the License
+# is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+# or implied.
diff --git a/python/nn4k/utils/config_parsing.py b/python/nn4k/utils/config_parsing.py
new file mode 100644
index 00000000..abc53849
--- /dev/null
+++ b/python/nn4k/utils/config_parsing.py
@@ -0,0 +1,56 @@
+# Copyright 2023 Ant Group CO., Ltd.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+# in compliance with the License. You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software distributed under the License
+# is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+# or implied.
+
+import json
+
+from typing import Any
+from typing import Union
+
+
+def preprocess_config(nn_config: Union[str, dict]) -> dict:
+    try:
+        if isinstance(nn_config, str):
+            with open(nn_config, "r") as f:
+                nn_config = json.load(f)
+    except:
+        raise ValueError("cannot decode config file")
+    return nn_config
+
+def get_field(nn_config: dict, name: str, text: str) -> Any:
+    value = nn_config.get(name)
+    if value is None:
+        message = "%s %r not found" % (text, name)
+        raise ValueError(message)
+    return value
+
+def get_string_field(nn_config: dict, name: str, text: str) -> str:
+    value = get_field(nn_config, name, text)
+    if not isinstance(value, str):
+        message = "%s %r must be string; " % (text, name)
+        message += "%r is invalid" % (value,)
+        raise TypeError(message)
+    return value
+
+def get_int_field(nn_config: dict, name: str, text: str) -> int:
+    value = get_field(nn_config, name, text)
+    if not isinstance(value, int):
+        message = "%s %r must be integer; " % (text, name)
+        message += "%r is invalid" % (value,)
+        raise TypeError(message)
+    return value
+
+def get_positive_int_field(nn_config: dict, name: str, text: str) -> int:
+    value = get_int_field(nn_config, name, text)
+    if value <= 0:
+        message = "%s %r must be positive integer; " % (text, name)
+        message += "%r is invalid" % (value,)
+        raise ValueError(message)
+    return value