Gradient monitor improvement

dht.py

@@ -90,14 +90,15 @@ class gradient_monitor(object):
         self.__last_time__ = None
 
     def process(self, value, time):
-        rv = True
         if self.__last_value__ is not None and self.__last_time__ is not None:
+            # Valid last value exists
             gradient = abs((value - self.__last_value__) / (time - self.__last_time__))
             if gradient > self.__max_gradient__:
-                rv = False
+                return False
+
         self.__last_value__ = value
         self.__last_time__ = time
-        return rv
+        return True
 
 
 class dht_22_monitor(object):