Fix code style.

roentgen/util.py

@@ -1,25 +1,34 @@
+"""
+Röntgen utility file.
+
+Author: Sergey Vartanov (me@enzet.ru).
+"""
+from dataclasses import dataclass
+from typing import Any
+
+
+@dataclass
 class MinMax:
     """
     Minimum and maximum.
     """
-    def __init__(self, min_=None, max_=None):
-        self.min_ = min_
-        self.max_ = max_
+    min_: Any = None
+    max_: Any = None
 
-    def update(self, value):
+    def update(self, value: Any) -> None:
         """
         Update minimum and maximum with new value.
         """
         self.min_ = value if not self.min_ or value < self.min_ else self.min_
         self.max_ = value if not self.max_ or value > self.max_ else self.max_
 
-    def delta(self):
+    def delta(self) -> Any:
         """
         Difference between maximum and minimum.
         """
         return self.max_ - self.min_
 
-    def center(self):
+    def center(self) -> Any:
         """
         Get middle point between minimum and maximum.
         """