diff --git a/quoracle/expr.py b/quoracle/expr.py
index 0890f62..20a44fd 100644
--- a/quoracle/expr.py
+++ b/quoracle/expr.py
@@ -7,7 +7,8 @@ import pulp
 class SupportsLessThan(Protocol):
     def __lt__(self, __other: Any) -> bool: ...
 
-T = TypeVar("T", bound=SupportsLessThan)
+
+T = TypeVar('T', bound=SupportsLessThan)
 
 
 def _min_hitting_set(sets: Iterator[Set]) -> int:
diff --git a/quoracle/quorum_system.py b/quoracle/quorum_system.py
index 90bb1f7..1950446 100644
--- a/quoracle/quorum_system.py
+++ b/quoracle/quorum_system.py
@@ -5,14 +5,14 @@ from .expr import Expr, Node, T
 from .geometry import Point, Segment
 from typing import (
     Any,
+    Callable,
     Dict,
-    Iterator,
+    FrozenSet,
     Generic,
+    Iterator,
     List,
     Optional,
     Set,
-    FrozenSet,
-    Callable,
     Tuple,
 )
 import collections
diff --git a/tests/test_expr.py b/tests/test_expr.py
index a5fb441..e5aad8e 100644
--- a/tests/test_expr.py
+++ b/tests/test_expr.py
@@ -1,7 +1,6 @@
-import unittest
-
 from quoracle.expr import Expr, Node, choose
 from typing import Any, List, Set, FrozenSet
+import unittest
 
 class TestExpr(unittest.TestCase):
     def test_quorums(self):