That looks perfect. Not sure which of dep or user it should be though...

Maybe the message for Series (but not DataFrames etc) should also mention this:

```
The truth value of a {0} is ambiguous. Use a.empty, a.item(), a.any() or a.all(). Currently, a boolean Series of length 1 is the exception.
```
and then the the User/Dep could have the same message ?