def invalid_dict_pickle_keys(self, msg_dict):
        """Return a list of keys that can't be pickled.  Return [] if 
        there are no pickling problems with the values associated with the
        keys.  Return the list of keys, if there are problems."""
        no_pickle_keys = list()
        for key, val in msg_dict.items():

            try:
                pickle.dumps(key)
                pickle.dumps(val)
            except TypeError:
                no_pickle_keys.append(key)  # This key has an unpicklable value
            except pickle.PicklingError:
                no_pickle_keys.append(key)  # This key has an unpicklable value
            except pickle.UnpickleableError:
                no_pickle_keys.append(key)  # This key has an unpicklable value

        return no_pickle_keys
Return a list of keys that can't be pickled.  Return [] if 
        there are no pickling problems with the values associated with the
        keys.  Return the list of keys, if there are problems.