diff --git a/pacs/utils/fit.py b/pacs/utils/fit.py
index 71df367..3a49021 100644
--- a/pacs/utils/fit.py
+++ b/pacs/utils/fit.py
@@ -1,5 +1,4 @@
 import multiprocessing as mp
-import subprocess
 from pathlib import Path
 
 from pacs.models.settings import MDsettings
@@ -55,7 +54,7 @@ def fit_mdtraj(settings: MDsettings, trj_file: str, out_file: str) -> None:
     parent = Path(trj_file).parent
     stem = Path(trj_file).stem
     fit_trj_file = (
-        f"{parent}/{stem}_fit{ext}" if out_file == None else f"{parent}/{out_file}"
+        f"{parent}/{stem}_fit{ext}" if out_file is None else f"{parent}/{out_file}"
     )
 
     ref_structure = settings.reference
diff --git a/pacs/utils/genfeature/genfeat.py b/pacs/utils/genfeature/genfeat.py
index cab064e..33ef2cb 100644
--- a/pacs/utils/genfeature/genfeat.py
+++ b/pacs/utils/genfeature/genfeat.py
@@ -22,7 +22,7 @@ def save(self, cycle: int, replica: int, features: np.ndarray) -> None:
             features,
         )
         LOGGER.info(
-            f"feature of trial{self.trial:03}cycle{cycle:03}replica{replica:03} was saved at {self.output_directory}/"
+            f"feature of trial{self.trial:03}cycle{cycle:03}replica{replica:03} was saved at {self.output_directory}/" # noqa B950
         )
 
     def prepare(self) -> None:
@@ -43,7 +43,7 @@ def cal_parallel(self, calc_feature, *args, **kwargs) -> None:
                     exit(1)
                 cycle = re.findall(r"(\d+)", str(path))[1]
                 replica = re.findall(r"(\d+)", str(path))[2]
-                trj_path = f"./trial{self.trial:03}/cycle{cycle:03}/replica{replica:03}/{self.trj_filename}"
+                trj_path = f"./trial{self.trial:03}/cycle{cycle:03}/replica{replica:03}/{self.trj_filename}" # noqa B950
 
                 future = executor.submit(calc_feature, trj_path, *args, **kwargs)
                 job_dict_list.append(
diff --git a/pacs/utils/parser.py b/pacs/utils/parser.py
index e7795ae..035435b 100644
--- a/pacs/utils/parser.py
+++ b/pacs/utils/parser.py
@@ -160,7 +160,7 @@ def parse(self) -> MDsettings:
             "--keep_selection",
             type=str,
             required=True,
-            help='selection of molecules to be retained in trajectory files. (e.g. "not water")',
+            help='selection to be retained in trajectory files. (e.g. "not water")',
         )
         parser_rmmol_mdtraj.add_argument(
             "-e",