lakeshore: remove leftover from an earlier attemt

class attribute 'classes' is not used

Change-Id: I80af00122c5faa9cd7c71bd9ffa4f40bf6a90164

frappy_psi/lakeshore.py

@@ -603,7 +603,6 @@ class Sensor(Base, Readable):
     channel = Property('used channel', StringType())  # input
     calcurve = Parameter('calibration curve name', StringType(), readonly=False)
     enabled = Parameter('enable flag', BoolType(), readonly=False)
-    classes = {}  # dict <model> of class
     curve_no = None
     STATUS_BIT_LABELS = 'invalid_reading old_reading b2 b3 t_under t_over units_zero units_overrange'.split()
     _read_error = None
@@ -720,7 +719,6 @@ class Sensor(Base, Readable):
 
 class Output(Base, HasControlledBy, Writable):
     """base class for heater output"""
-    classes = {}  # dict <model> of dict <output_no> of class
     value = Parameter('heater output', FloatRange(0, 100, unit='W'))
     target = Parameter('manual heater output', FloatRange(0, 100, unit='W'), default=0)
     htr = Parameter('heater output current percentage', FloatRange(0, 100, unit='%'))
@@ -966,13 +964,6 @@ class Loop(HasConvergence, HasOutputModule, Sensor):
     }, prefix='pid_', readonly=False)
     power_offset = Parameter('power offset\n\n(using LakeShores Manual Output)',
                              FloatRange(0, 100, unit='W'), readonly=False, default=0)
-    classes = {}
-
-    def __init_subclass__(cls):
-        super().__init_subclass__()
-        if cls.model:  # do not register abstract base classes
-            cls.model = str(cls.model)
-            cls.classes[cls.model] = cls
 
     def write_ctrlpars(self, pid):
         pid = self.command(f'PID {self.output_module.output_no}', *[pid[k] for k in 'pid'])