code: def isModified(self):
          
          # NOTE: only check content digest if locally cached content is set
          # (content already pulled or new content set); otherwise this
          # results in pulling content down to checksum it !
          return self.info_modified or \
              self._content and self._content_digest() != self.digest
docs: Check if either the datastream content or profile fields have changed
          and should be saved to Fedora.
  
          :rtype: boolean