Add types to pre-commit

pre_commit/meta_hooks/identity.py

@@ -1,12 +1,15 @@
 import sys
+from typing import Optional
+from typing import Sequence
 
 from pre_commit import output
 
 
-def main(argv=None):
+def main(argv: Optional[Sequence[str]] = None) -> int:
     argv = argv if argv is not None else sys.argv[1:]
     for arg in argv:
         output.write_line(arg)
+    return 0
 
 
 if __name__ == '__main__':