diff --git a/.gitignore b/.gitignore
index adfae9cc..83dc99d5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -112,4 +112,4 @@ dpl/output/
 .viminfo
 
 # inner egs
-inner
+delta_inner
diff --git a/docs/development/contributing.md b/docs/development/contributing.md
index ffe45a6d..57d6e098 100644
--- a/docs/development/contributing.md
+++ b/docs/development/contributing.md
@@ -35,9 +35,9 @@ Before commit golang code, plase using `go fmt` and `go vec` to format and lint
 
 ## Logging guideline
 
-For `python` using [abseil-py](https://github.com/abseil/abseil-py). 
+For `python` using [abseil-py](https://github.com/abseil/abseil-py), [more info](https://abseil.io/docs/python/).
 
-For C++ using [abseil-cpp](https://github.com/abseil/abseil-cpp).
+For C++ using [abseil-cpp](https://github.com/abseil/abseil-cpp), [more info](https://abseil.io/docs/cpp/).
 
 For Golang using [glog](https://github.com/golang/glog).
 
diff --git a/utils/pb_pbtxt.py b/utils/pb_pbtxt.py
index e5147753..1d2be4de 100755
--- a/utils/pb_pbtxt.py
+++ b/utils/pb_pbtxt.py
@@ -65,8 +65,10 @@ def main(_):
   logging.info(f"dump graph to {dump_dir}")
 
 if __name__ == '__main__':
+  # flags usage: https://abseil.io/docs/python/guides/flags
   logging.set_verbosity(logging.INFO)
-  flags.DEFINE_string('graph', default=None, help='graph.pb file name')
-  flags.DEFINE_bool('binary_in', default=True, help='input graph is binary or not')
+  flags.DEFINE_string('graph', default=None, help='graph.pb file name', short_name='g')
+  flags.DEFINE_bool('binary_in', default=True, help='input graph is binary or not', short_name='b')
+  flags.mark_flag_as_required('graph')
 
   app.run(main)
diff --git a/utils/run_saved_model.py b/utils/run_saved_model.py
index d4be979e..3dab707b 100755
--- a/utils/run_saved_model.py
+++ b/utils/run_saved_model.py
@@ -17,6 +17,7 @@
 ''' Saved & Frozen & Checkpoint model Evaluater'''
 import os
 from absl import logging
+from absl import flags
 from absl import app
 
 from delta import utils
@@ -59,10 +60,12 @@ def main(_):
 def define_flags():
   ''' define flags for evaluator'''
   # The GPU devices which are visible for current process
-  app.flags.DEFINE_string('gpu', '', 'same to CUDA_VISIBLE_DEVICES')
-  app.flags.DEFINE_string('config', 'conf/xxx.yml', help='path to yaml config file')
-  app.flags.DEFINE_string('mode', 'eval', 'one of eval, infer, eval_and_infer')
-  app.flags.DEFINE_boolean('debug', False, 'debug mode')
+  flags.DEFINE_string('gpu', '', 'same to CUDA_VISIBLE_DEVICES')
+  flags.DEFINE_string('config', None, help='path to yaml config file')
+  flags.DEFINE_enum('mode', 'eval',['eval', 'infer', 'eval_and_infer'], 'eval or infer')
+  flags.DEFINE_bool('debug', False, 'debug mode')
+  # https://github.com/abseil/abseil-py/blob/master/absl/flags/_validators.py#L330
+  flags.mark_flags_as_required(['config', 'mode'])
 
 if __name__ == '__main__':
   logging.set_verbosity(logging.INFO)