How to remove the " punctuation using .to_csv method?
I have a data frame as below:

```
#user    item   rating  time    word_count  review
3        2      4.0     131600  123         1 1 3 3 3 4 4 5 ..
......
```

The number in review denotes the word_id. When I apply the `to_csv` function:

```
df.to_csv("data.votes", sep = " ", cols = ['user','item','rating','time','word count','review'], header = False, index = False)
```

The resulting text file is like:

```
3 2 4.0 131600 123 "1 1 3 3 3 4 4 5...  101 "
```

How can I remove the annoying `"` ? It has a bad effect on running my model. Thank you in advance!
