frappy_psi.motorvalve: move doc string to class

- this will allow to add other classes if needed

Change-Id: I452c2be19456829796d899891719f5659fac2ba9

frappy_psi/motorvalve.py

@@ -19,6 +19,15 @@
 #
 # *****************************************************************************
 
+
+from frappy.core import Drivable, Parameter, EnumType, Attached, FloatRange, \
+    Command, IDLE, BUSY, WARN, ERROR, PersistentParam, PersistentMixin
+from frappy.errors import HardwareError
+from frappy_psi.trinamic import Motor
+from frappy.lib.statemachine import StateMachine, Retry, Stop
+
+
+class MotorValve(PersistentMixin, Drivable):
     """motor valve using a trinamic PD-1161 motor
 
     the valve has an end switch connected to the 'home' digital input
@@ -41,15 +50,6 @@ turns = 9      # number of turns needed to open fully
     speed = 400    # close to max. speed
     lowspeed = 50  # speed for final closing / reference run
     """
-
-from frappy.core import Drivable, Parameter, EnumType, Attached, FloatRange, \
-    Command, IDLE, BUSY, WARN, ERROR, PersistentParam, PersistentMixin
-from frappy.errors import HardwareError
-from frappy_psi.trinamic import Motor
-from frappy.lib.statemachine import StateMachine, Retry, Stop
-
-
-class MotorValve(PersistentMixin, Drivable):
     motor = Attached(Motor)
     value = Parameter('current state', EnumType(
         closed=0, opened=1, undefined=-1), default=-1, update_unchanged='never')