There is even a comment in `as_relational()` that this can be done better:
```
--> 676         if self.is_left_unbounded and self.is_right_unbounded:
    677             return True  # XXX: Contained(symbol, Floats)
```
Just instead of `Floats` there should be `Reals` (too much sed when `Real` was renamed to `Float`).