trivial modify for type hint and variable name

sohstationviewer/view/db_config/value_color_helper/edit_value_color_dialog/multi_color_dot_dialog.py

 import sys
 import platform
 import os
-from typing import List, Dict
+from typing import List, Dict, Optional
 
 from PySide2 import QtWidgets, QtCore, QtGui
 from PySide2.QtWidgets import QWidget
@@ -23,14 +23,14 @@ class BoundValidator(QtGui.QValidator):
     Value '-'  to allow typing negative float. If user type '-' only, it will
         be checked when editing is finished.
     """
-    def validate(self, input, pos):
-        if input in ['', '-']:
+    def validate(self, input_val, pos):
+        if input_val in ['', '-']:
             return QtGui.QValidator.Acceptable
         try:
-            input = float(input)
+            input_val = float(input_val)
         except ValueError:
             return QtGui.QValidator.Invalid
-        if -10 <= input <= 10:
+        if -10 <= input_val <= 10:
             return QtGui.QValidator.Acceptable
         else:
             return QtGui.QValidator.Invalid
@@ -38,7 +38,8 @@ class BoundValidator(QtGui.QValidator):
 
 class MultiColorDotDialog(EditValueColorDialog):
     def __init__(
-            self, parent: QWidget, value_color_str: str, upper_equal: bool):
+            self, parent: Optional[QWidget],
+            value_color_str: str, upper_equal: bool):
         """
         Dialog to edit color for Multi-color Dot Plot