backends: Make the filter_class an abstractproperty

diff --git a/tasklib/backends.py b/tasklib/backends.py
index fe24fd205d521c64214418afd7bb0c64b30b07df..0d01470c123208ca39cb017877c94c754bb6e45c 100644 (file)
--- a/tasklib/backends.py
+++ b/tasklib/backends.py
@@ -22,7 +22,10 @@ VERSION_2_4_5 = six.u('2.4.5')
 
 class Backend(object):
 
-    filter_class = TaskWarriorFilter
+    @abc.abstractproperty
+    def filter_class(self):
+        """Returns the TaskFilter class used by this backend"""
+        pass
 
     @abc.abstractmethod
     def filter_tasks(self, filter_obj):
@@ -208,6 +211,10 @@ class TaskWarrior(object):
                              "datetime, its type is not supported: {}"
                              .format(type(value)))
 
+    @property
+    def filter_class(self):
+        return TaskWarriorFilter
+
     # Public interface
 
     def get_config(self):