Use callback id() instead of frame hash() to identify anonymous python streams

Frame hashes are not unique since the frame isn't kept around for the
life time of the stream.

Fixes #292.

mpv.py

@@ -1956,6 +1956,10 @@ class MPV(object):
         Any given name can only be registered once. The catch-all can also only be registered once. To unregister a
         stream, call the .unregister function set on the callback.
 
+        If name is None (the default), a name and corresponding python:// URI are automatically generated. You can
+        access the name through the .stream_name property set on the callback, and the stream URI for passing into
+        mpv.play(...) through the .stream_uri property.
+
         The generator signals EOF by returning, manually raising StopIteration or by yielding b'', an empty bytes
         object.
 
@@ -1972,16 +1976,25 @@ class MPV(object):
         reader.unregister()
         """
         def register(cb):
+            nonlocal name
+            if name is None:
+                name = f'__python_mpv_anonymous_python_stream_{id(cb)}__'
+
             if name in self._python_streams:
                 raise KeyError('Python stream name "{}" is already registered'.format(name))
+
             self._python_streams[name] = (cb, size)
             def unregister():
                 if name not in self._python_streams or\
                         self._python_streams[name][0] is not cb: # This is just a basic sanity check
                     raise RuntimeError('Python stream has already been unregistered')
                 del self._python_streams[name]
+
             cb.unregister = unregister
+            cb.stream_name = name
+            cb.stream_uri = f'python://{name}'
             return cb
+
         return register
 
     @contextmanager
@@ -2003,10 +2016,8 @@ class MPV(object):
         """
         q = queue.Queue()
 
-        frame = sys._getframe()
-        stream_name = f'__python_mpv_play_generator_{hash(frame)}'
-        EOF = frame # Get some unique object as EOF marker
-        @self.python_stream(stream_name)
+        EOF = object() # Get some unique object as EOF marker
+        @self.python_stream()
         def reader():
             while (chunk := q.get()) is not EOF:
                 if chunk:
@@ -2017,21 +2028,19 @@ class MPV(object):
             q.put(chunk)
 
         # Start playback before yielding, the first call to reader() will block until write is called at least once.
-        self.play(f'python://{stream_name}')
+        self.play(reader.stream_uri)
         yield write
         q.put(EOF)
 
     def play_bytes(self, data):
         """ Play the given bytes object as a single file. """
-        frame = sys._getframe()
-        stream_name = f'__python_mpv_play_generator_{hash(frame)}'
 
-        @self.python_stream(stream_name)
+        @self.python_stream()
         def reader():
             yield data
             reader.unregister() # unregister itself
 
-        self.play(f'python://{stream_name}')
+        self.play(reader.stream_uri)
 
     def python_stream_catchall(self, cb):
         """ Register a catch-all python stream to be called when no name matches can be found. Use this decorator on a