- redefine activate method

- for task introduced open() conext method

components/aheater.py

@@ -1,5 +1,6 @@
 import abc
 from utils.value import AttributeChange
+from contextlib import contextmanager
 
 
 class AHeater(AttributeChange):
@@ -14,6 +15,16 @@ class AHeater(AttributeChange):
 	def get_power_max(self):
 		pass
 
+	@contextmanager
+	def open(self):
+		try:
+			self.activate(True)
+			yield None
+		finally:
+			self.activate(False)
+
+		return None
+
 	@abc.abstractmethod
 	def activate(self, enable):
 		return None