Update __init__.py

Author: Pwhsky

deeptrack/test/__init__.py

@@ -1,4 +1,5 @@
 from .backend import *
+from .extras import *
 from .test_aberrations import *
 from .test_augmentations import *
 from .test_elementwise import *
@@ -16,4 +17,4 @@
 from .test_scatterers import *
 from .test_sequences import *
 from .test_statistics import *
-from .test_utils import *
+from .test_utils import *