Use Union for Python 3.8 compatibility

robyn/reloader.py

@@ -4,7 +4,7 @@
 import subprocess
 import sys
 import time
-from typing import List
+from typing import List, Union
 
 from watchdog.events import FileSystemEventHandler
 from watchdog.observers import Observer
@@ -115,7 +115,7 @@ class EventHandler(FileSystemEventHandler):
     def __init__(self, file_path: str, directory_path: str) -> None:
         self.file_path = file_path
         self.directory_path = directory_path
-        self.process: subprocess.Popen[bytes] | None = None  # Keep track of the subprocess
+        self.process: Union[subprocess.Popen[bytes], None] = None  # Keep track of the subprocess
         self.built_rust_binaries: List = []  # Keep track of the built rust binaries
 
         self.last_reload = time.time()  # Keep track of the last reload. EventHandler is initialized with the process.