More renamings

nifty4/models/__init__.py

-from .constant import ConstantModel
+from .constant import Constant
 from .local_nonlinearity import LocalModel
 from .model import LinearModel, Model
-from .position import PositionModel
+from .variable import Variable
 
-__all__ = ['Model', 'ConstantModel', 'LocalModel', 'PositionModel',
+__all__ = ['Model', 'Constant', 'LocalModel', 'Variable',
            'LinearModel']

nifty4/models/constant.py

@@ -2,9 +2,9 @@ from ..operators import MultiSkyGradientOperator
 from .model import Model
 
 
-class ConstantModel(Model):
+class Constant(Model):
     def __init__(self, position, constant):
-        super(ConstantModel, self).__init__(position)
+        super(Constant, self).__init__(position)
         self._constant = constant
 
         self._value = self._constant

nifty4/models/position.py → nifty4/models/variable.py

@@ -3,12 +3,12 @@ import nifty4 as ift
 from .model import Model
 
 
-class PositionModel(Model):
+class Variable(Model):
     """
     Returns the MultiField.
     """
     def __init__(self, position):
-        super(PositionModel, self).__init__(position)
+        super(Variable, self).__init__(position)
 
         self._value = position
         self._gradient = ift.ScalingOperator(1., position.domain)