How to use the bugwarrior.db.merge_left function in bugwarrior

def assertMerged(self, local, remote, **kwargs):
        db.merge_left('annotations', local, remote, **kwargs)
        self.assertEqual(local, remote)

def test_rough_equality_hamming_true(self):
        """ When hamming=True, rough equivalents are not duplicated. """
        remote = {'annotations': ['\n  testing  \n']}

        db.merge_left('annotations', self.issue_dict, remote, hamming=True)
        self.assertEqual(len(self.issue_dict['annotations']), 1)

def test_rough_equality_hamming_false(self):
        """ When hamming=False, rough equivalents are duplicated. """
        remote = {'annotations': ['\n  testing  \n']}

        db.merge_left('annotations', self.issue_dict, remote, hamming=False)
        self.assertEqual(len(self.issue_dict['annotations']), 2)