diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 4999367..9b26d29 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -2,7 +2,7 @@ exclude: |
     (?x)^(
         README.md|
         LICENSE|
-        tests/ymls/
+        tests/ymls/others/
     )
 repos:
     - repo: https://github.com/pre-commit/pre-commit-hooks
diff --git a/compose_viz/graph.py b/compose_viz/graph.py
index c686e3c..15516ca 100644
--- a/compose_viz/graph.py
+++ b/compose_viz/graph.py
@@ -1,3 +1,5 @@
+from typing import Optional
+
 import graphviz
 
 from compose_viz.compose import Compose
@@ -38,11 +40,11 @@ def apply_edge_style(type) -> dict:
         "depends_on": {
             "style": "dotted",
         },
-        "extends":{
+        "extends": {
             "dir": "both",
             "arrowhead": "inv",
             "arrowtail": "dot",
-        }
+        },
     }
 
     return style[type]
@@ -60,10 +62,10 @@ class Graph:
         transTable = name.maketrans({":": ""})
         return name.translate(transTable)
 
-    def add_vertex(self, name: str, type: str, lable: str = None) -> None:
+    def add_vertex(self, name: str, type: str, lable: Optional[str] = None) -> None:
         self.dot.node(self.validate_name(name), lable, **apply_vertex_style(type))
 
-    def add_edge(self, head: str, tail: str, type: str, lable: str = None) -> None:
+    def add_edge(self, head: str, tail: str, type: str, lable: Optional[str] = None) -> None:
         self.dot.edge(self.validate_name(head), self.validate_name(tail), lable, **apply_edge_style(type))
 
     def render(self, format: str, cleanup: bool = True) -> None: