old_contents: from dimagi.utils.mixins import UnicodeMixIn
  
  class Change(UnicodeMixIn):
      """
      Represents a single line from the _changes feed, for easier processing
      """
      
      def __init__(self, line):
          self.line = line
          self.id = line.get("id", None)
          self.seq = line.get("seq", None)
          self.changes = line.get("changes", [])
          self.deleted = "deleted" in line and line["deleted"]
          
      @property
      def rev(self):
          if self.changes and self.changes[0] and "rev" in self.changes[0]:
              return self.changes[0]["rev"]
          return None
      
      def __unicode__(self):
          return str(self.line)
new_contents: from dimagi.utils.mixins import UnicodeMixIn
  from couchdbkit.resource import ResourceNotFound
  
  class Change(UnicodeMixIn):
      """
      Represents a single line from the _changes feed, for easier processing
      """
      
      def __init__(self, line):
          self.line = line
          self.id = line.get("id", None)
          self.seq = line.get("seq", None)
          self.changes = line.get("changes", [])
          self.deleted = "deleted" in line and line["deleted"]
          
      @property
      def rev(self):
          if self.changes and self.changes[0] and "rev" in self.changes[0]:
              return self.changes[0]["rev"]
          return None
      
      def __unicode__(self):
          return str(self.line)
      
      
      def is_current(self, db):
          """Is this change pointing at the current rev in the DB?"""
          if self.rev:
              try:
                  return db.get_rev(self.id) == self.rev
              except ResourceNotFound:
                  # this doc has been deleted.  clearly an old rev
                  return False
          # we don't know if we don't know the rev
          # what's the appropriate failure mode? 
          # I think treating things like they are current is appropraite 
          # e.g. "you might want to act on this"
          return True
  
  
subject: add is_current field to change object