ls331: Add method to set heater power

ls331.py

@@ -148,6 +148,11 @@ class LS331:
         r = self.ask(b'HTR?')
         return float(r)
 
+    def set_heater(self, loop, value):
+        """Set heater power."""
+        assert loop == 1 or loop == 2
+        self.send(b'MOUT %d,%f' % (loop, value))
+
     def get_setpoint(self, loop):
         """Temperature control loop setpoint."""
         assert loop == 1 or loop == 2