[DOC] add explicit imports to try and fix sphynx warnings in nightlies

bob/ip/stereo/stereo_stream_filters.py

@@ -83,7 +83,7 @@ from .parameters import StereoParameters
 from .stereo import stereo_match, reproject_image
 from .camera import CameraPair
 
-from bob.io.stream import StreamArray
+from bob.io.stream import StreamArray, Stream, StreamFilter, stream_filter
 
 import numpy as np