code: def _DetermineFormat(self):
      
      if self._zip:
        # If zip was passed to __init__ then path isn't used
        assert not self._path
        return True
  
      if not isinstance(self._path, basestring) and hasattr(self._path, 'read'):
        # A file-like object, used for testing with a StringIO file
        self._zip = zipfile.ZipFile(self._path, mode='r')
        return True
  
      if not os.path.exists(self._path):
        self._problems.FeedNotFound(self._path)
        return False
  
      if self._path.endswith('.zip'):
        try:
          self._zip = zipfile.ZipFile(self._path, mode='r')
        except IOError:  # self._path is a directory
          pass
        except zipfile.BadZipfile:
          self._problems.UnknownFormat(self._path)
          return False
  
      if not self._zip and not os.path.isdir(self._path):
        self._problems.UnknownFormat(self._path)
        return False
  
      return True
docs: Determines whether the feed is in a form that we understand, and
         if so, returns True.