omit graphlib from test coverage (#874)

Author: sinisaos

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.black]
 line-length = 79
-target-version = ['py37', 'py38', 'py39', 'py310']
+target-version = ['py38', 'py39', 'py310']
 
 [tool.isort]
 profile = "black"
@@ -31,7 +31,8 @@ markers = [
 omit = [
     "*.jinja",
     "**/piccolo_migrations/*",
-    "**/piccolo_app.py"
+    "**/piccolo_app.py",
+    "**/utils/graphlib/*",
 ]
 
 [tool.coverage.report]