'Ensure that push with position works properly for an instance.'

@needs_mongodb_v26
def test_push_with_position(self):

    class BlogPost(Document, ):
        slug = StringField()
        tags = ListField(StringField())
    blog = BlogPost()
    blog.slug = 'ABC'
    blog.tags = ['python']
    blog.save()
    blog.update(push__tags__0=['mongodb', 'code'])
    blog.reload()
    self.assertEqual(blog.tags, ['mongodb', 'code', 'python'])
