Pandas eval/query doesn't match whole words
This here works when looking for whole words with \b
```python
# Your code here
df = pd.DataFrame({'b' : ['hif das', 'foodas', 'fat', 'cat']})
df[df.b.str.contains(r'\bdas\b')]
```
But this doesn't work:
```python
df[df.eval('b.str.contains(r"\bdas\b")', engine="python", parser="python")]
df.query('b.str.contains(r"\bdas\b")', engine="python")
```

query() and eval() functions are useful for non-programmers writing just sql code and you load it in query(). I don't see any reason why you couldn't use \b inside query or eval, since you can use other characters like | or ^ or \s

Expected Output:

```
        b
0	hif das
```
