remove ITrainer interface since parameters for train is already getting out of sync. Currently there is no benefit of having a interface.

python/paddle/v2/trainer.py

@@ -8,7 +8,7 @@ from . import event as v2_event
 from . import optimizer as v2_optimizer
 from . import parameters as v2_parameters
 
-__all__ = ['ITrainer', 'SGD']
+__all__ = ['SGD']
 
 
 def default_event_handler(event):
@@ -22,26 +22,7 @@ def default_event_handler(event):
     pass
 
 
-class ITrainer(object):
-    """
-    The interface of Trainer. The only exposed method is `train`.
-    """
-
-    def train(self, reader, topology, parameters, event_handler=None):
-        """
-        train method.
-
-        :param reader:
-        :param topology:
-        :param parameters:
-        :param event_handler:
-        :return:
-        """
-
-        raise NotImplementedError()
-
-
-class SGD(ITrainer):
+class SGD():
     def __init__(self, cost, parameters, update_equation):
         """
         Simple SGD Trainer.