Upgraded make_composite_func so that it can optionally return values

comsdk/edge.py

@@ -364,8 +364,14 @@ def make_dump(dump_name_format, format_keys=(), omit=None, method='pickle'):
 
 def make_composite_func(*funcs):
     def _composite(d):
+        res = None
         for func in funcs:
-            func(d)
+            f_res = func(d)
+            # this trick allows us to combine returning
+            # and non-returning functions
+            if f_res is not None:
+                res = f_res
+        return res
     return _composite