len(flipped_images)is six in this case, and flipped_images >> cube_map does not give an error, however you do get this error on update: vtkOpenGLTexture.cxx:151 ERR| vtkOpenGLTexture (0x283e630): Cube Maps require 6 inputs.
I naively thought it would work in a manner analogous to that in vtkAppendFilter, but it seems six separate intput ports are required.
So probably not worth worrying about as you would have to warn that exactly six inputs are required in a specific order.
I guess this is why flipped_images >> cube_map doesn´t work in this case:
“SetInputConnection(self, input:vtkAlgorithmOutput) → None C++: virtual void SetInputConnection(vtkAlgorithmOutput *input)
Set the connection for the given input port index. Each input port of a filter has a specific purpose. A port may have zero or more connections and the required number is specified by each filter. Setting the connection with this method removes all other connections from the port. To add more than one connection use AddInputConnection().”