def _heads(self, reverse=False):
        refs = self._repo.get_refs()
        heads = {}

        for key, val in refs.items():
            for ref_key in ['refs/heads/', 'refs/remotes/origin/']:
                if key.startswith(ref_key):
                    n = key[len(ref_key):]
                    if ['HEAD'] not in n:
                        heads[n] = val

        return heads if reverse else dict((y, x) for x, y in heads.iteritems())
dataset/ETHPy150Open codeinn/vcs/vcs/backends/git/repository.py/GitRepository._heads/swapped operands of `not in`