Parens needed in Python 3.6

src/calng/utils.py

@@ -39,7 +39,7 @@ def threadsafe_cache(fun):
     return aux
 
 
-@functools.lru_cache
+@functools.lru_cache()
 def transpose_order(axes_in, axes_out):
     """Computes the order of axes_out relative to axes_in for transposition purposes