fix:rank.sum docstring

skimage/filter/rank/generic.py

@@ -528,8 +528,7 @@ def pop(image, selem, out=None, mask=None, shift_x=False, shift_y=False):
                   mask=mask, shift_x=shift_x, shift_y=shift_y)
 
 def sum(image, selem, out=None, mask=None, shift_x=False, shift_y=False):
-    """Return the sum of pixels inside the neighborhood.
-    If sum does not fit the data type,folding is possible.
+    """Return the sum of pixels inside the neighborhood (truncated to uint8 or uint16).
 
     Parameters
     ----------