pymongo insert

```
#### 1
def process_item(self, item, spider):
        name = item.collection
        self.db[name].insert(dict(item))
        return item
#### 2
def process_item(self, item, spider):
        name = item.collection
        self.db[name].insert_one(dict(item))
        return item
```
in MongoPipeline code 1 is incorrect，code 2 works fine