add back-compat for triggerable

tensorpack/callbacks/base.py

@@ -7,7 +7,7 @@ from abc import ABCMeta
 import six
 from ..tfutils.common import get_op_or_tensor_by_name
 
-__all__ = ['Callback', 'ProxyCallback', 'CallbackFactory']
+__all__ = ['Callback', 'ProxyCallback', 'CallbackFactory', 'Triggerable']
 
 
 @six.add_metaclass(ABCMeta)
@@ -161,6 +161,10 @@ class Callback(object):
         return type(self).__name__
 
 
+# back-compat. in case someone write something in triggerable
+Triggerable = Callback
+
+
 class ProxyCallback(Callback):
     """ A callback which proxy all methods to another callback.
         It's useful as a base class of callbacks which decorate other callbacks.