Small beautifications

mpv.py

@@ -229,10 +229,7 @@ _handle_func('mpv_get_wakeup_pipe', [], c_int)
 
 class ynbool:
     def __init__(self, val=False):
-		if not val or val == b'no' or val == 'no':
-			self.val = False
-		else:
-			self.val = True
+        self.val = bool(val and val not in (b'no', 'no'))
 
     def __nonzero__(self):
         return self.val
@@ -419,12 +416,13 @@ class MPV:
     
     @property
     def metadata(self):
-		...
+        raise NotImplementedError
+
     def chapter_metadata(self):
-		...
+        raise NotImplementedError
 
     def vf_metadata(self):
-		...
+        raise NotImplementedError
     
     # Convenience functions
     def play(self, filename):