docs: def diff_iter(self, other, **kwargs):
          """Generator method which returns the differences from the invocant to
          the argument.  This specializes :py:meth:`Record.diff_iter` by
          returning :py:class:`JsonDiffInfo` objects.
          """
          for diff in super(JsonRecord, self).diff_iter(other, **kwargs):
              # TODO: object copy/upgrade constructor
              newargs = diff.__getstate__()
              yield JsonDiffInfo(**(newargs))