importmatplotlib.pyplotaspltfrommatplotlib.collectionsimportQuadMeshimportnumpyasnpx,y=np.linspace([-1.5,-1.5], [1.5,1.5],20).TX,Y=np.meshgrid(x,y)coll=QuadMesh(np.stack((X,Y),axis=2))f,ax=plt.subplots()ax.add_collection(coll)

TypeError: 'NoneType' object is not subscriptableTraceback (most recent call last):  File "...\matplotlib\cbook\__init__.py", line 287, in process    func(*args, **kwargs)  File "...\matplotlib\backend_bases.py", line 3061, in mouse_move    s = self._mouse_event_to_message(event)  File "...\matplotlib\backend_bases.py", line 3051, in _mouse_event_to_message    data = a.get_cursor_data(event)  File "...\matplotlib\collections.py", line 2214, in get_cursor_data    return self.get_array()[ind]TypeError: 'NoneType' object is not