hints for player names, flake8, rankgraph ded

tests/test_parser.py

@@ -1,8 +1,7 @@
 import os
-from unittest.mock import MagicMock, patch
+from unittest.mock import MagicMock
 
 from katrain.core.base_katrain import KaTrainBase
-from katrain.core.engine import KataGoEngine
 from katrain.core.game import Game, KaTrainSGF
 from katrain.core.sgf_parser import SGF, SGFNode
 
@@ -107,7 +106,7 @@ def test_old_server_style():
 
 def test_ogs():
     file = os.path.join(os.path.dirname(__file__), "data/ogs.sgf")
-    tree = SGF.parse_file(file)
+    SGF.parse_file(file)
 
 
 def test_gibo():