Improve PEP8 adherance using flake8 linter

src/pg_rad/exceptions/exceptions.py

@@ -1,8 +1,10 @@
 class ConvergenceError(Exception):
     """Raised when an algorithm fails to converge."""
 
+
 class DataLoadError(Exception):
     """Base class for data loading errors."""
 
+
 class InvalidCSVError(DataLoadError):
-    """Raised when a file is not a valid CSV."""
+    """Raised when a file is not a valid CSV."""