diff --git a/fastNLP/core/utils.py b/fastNLP/core/utils.py
index 82e3d07c..efc2ef7e 100644
--- a/fastNLP/core/utils.py
+++ b/fastNLP/core/utils.py
@@ -3,9 +3,9 @@ import inspect
 import os
 from collections import Counter
 from collections import namedtuple
-from collections import defaultdict
 import torch
 
+CheckRes = namedtuple('CheckRes', ['missing', 'unused', 'duplicated', 'required', 'all_needed'], verbose=False)
 def save_pickle(obj, pickle_path, file_name):
     """Save an object into a pickle file.
 
@@ -121,14 +121,11 @@ def _check_arg_dict_list(func, args):
     missing = list(require_args - input_args)
     unused = list(input_args - all_args)
 
-    check_res = {}
-    check_res['missing'] = missing
-    check_res['unused'] = unused
-    check_res['duplicated'] = duplicated
-    check_res['required'] = list(require_args)
-    check_res['all_needed'] = list(all_args)
-
-    return check_res
+    return CheckRes(missing=missing,
+                    unused=unused,
+                    duplicated=duplicated,
+                    required=list(require_args),
+                    all_needed=list(all_args))
 
 def get_func_signature(func):
     """
@@ -165,6 +162,19 @@ def get_func_signature(func):
         signature_str = func.__name__ + signature_str
         return signature_str
 
+def _is_function_or_method(func):
+    """
+
+    :param func:
+    :return:
+    """
+    if not inspect.ismethod(func) and not inspect.isfunction(func):
+        return False
+    return True
+
+def _check_function_or_method(func):
+    if not _is_function_or_method(func):
+        raise TypeError(f"{type(func)} is not a method or function.")
 
 def _syn_model_data(model, *args):
     """
@@ -204,3 +214,19 @@ def _move_dict_value_to_device(device, *args):
         else:
             raise TypeError("Only support `dict` type right now.")
 
+
+class CheckError(Exception):
+    """
+
+    CheckError. Used in losses.LossBase, metrics.MetricBase.
+    """
+    def __init__(self, check_res):
+        err = ''
+        if check_res['missing']:
+            err += f"Missing: {check_res['missing']}\n"
+        if check_res['duplicated']:
+            err += f"Duplicated: {check_res['duplicated']}\n"
+        if check_res['unused']:
+            err += f"Unused: {check_res['unused']}\n"
+        Exception.__init__(self, err)
+        self.check_res = check_res