old_contents: # -*- coding: utf-8 -*-
  
  # vim: tabstop=4 shiftwidth=4 softtabstop=4
  
  #    Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
  #
  #    Licensed under the Apache License, Version 2.0 (the "License"); you may
  #    not use this file except in compliance with the License. You may obtain
  #    a copy of the License at
  #
  #         http://www.apache.org/licenses/LICENSE-2.0
  #
  #    Unless required by applicable law or agreed to in writing, software
  #    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  #    License for the specific language governing permissions and limitations
  #    under the License.
  
  import abc
  
  
  class Task(object):
      """An abstraction that defines a potential piece of work that can be
      applied and can be reverted to undo the work as a single unit.
      """
      __metaclass__ = abc.ABCMeta
  
      def __init__(self, name=None):
          if name is None:
              name = "%s: %s" % (self.__class__.__name__, id(self))
          self.name = name
  
      def __str__(self):
          return self.name
  
      def requires(self):
          """Return any input 'resource' names this task depends on existing
          before this task can be applied."""
          return set()
  
      def provides(self):
          """Return any output 'resource' names this task produces that other
          tasks may depend on this task providing."""
          return set()
  
      @abc.abstractmethod
      def apply(self, context, *args, **kwargs):
          """Activate a given task which will perform some operation and return.
  
             This method can be used to apply some given context and given set
             of args and kwargs to accomplish some goal. Note that the result
             that is returned needs to be serializable so that it can be passed
             back into this task if reverting is triggered."""
          raise NotImplementedError()
  
      def revert(self, context, result, cause):
          """Revert this task using the given context, result that the apply
             provided as well as any information which may have caused
             said reversion."""
          pass
  
new_contents: # -*- coding: utf-8 -*-
  
  # vim: tabstop=4 shiftwidth=4 softtabstop=4
  
  #    Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
  #
  #    Licensed under the Apache License, Version 2.0 (the "License"); you may
  #    not use this file except in compliance with the License. You may obtain
  #    a copy of the License at
  #
  #         http://www.apache.org/licenses/LICENSE-2.0
  #
  #    Unless required by applicable law or agreed to in writing, software
  #    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  #    License for the specific language governing permissions and limitations
  #    under the License.
  
  import abc
  
  
  class Task(object):
      """An abstraction that defines a potential piece of work that can be
      applied and can be reverted to undo the work as a single unit.
      """
      __metaclass__ = abc.ABCMeta
  
      def __init__(self, name=None):
          if name is None:
              name = "%s: %s" % (self.__class__.__name__, id(self))
          self.name = name
  
      def __str__(self):
          return "Task: %s" % (self.name)
  
      def requires(self):
          """Return any input 'resource' names this task depends on existing
          before this task can be applied."""
          return set()
  
      def provides(self):
          """Return any output 'resource' names this task produces that other
          tasks may depend on this task providing."""
          return set()
  
      @abc.abstractmethod
      def apply(self, context, *args, **kwargs):
          """Activate a given task which will perform some operation and return.
  
             This method can be used to apply some given context and given set
             of args and kwargs to accomplish some goal. Note that the result
             that is returned needs to be serializable so that it can be passed
             back into this task if reverting is triggered."""
          raise NotImplementedError()
  
      def revert(self, context, result, cause):
          """Revert this task using the given context, result that the apply
             provided as well as any information which may have caused
             said reversion."""
          pass
  
subject: Add a more useful name that shows this is a task.