There's an extra space between ```ValueError``` and ```(```- please remove. You also don't need to use ```\``` since the string is inside of parens. Please also add a space between ```Invalid value:``` and the interpolated value.

The error message is a little misleading, since alpha diversity values can be greater than 1 (this depends on the metric of course). The check being performed in this function is to verify that a valid normalized alpha diversity value is provided. I'd update the message to be something like:

```
raise ValueError("Encountered invalid normalized alpha diversity value %s. Normalized values must be between 0 and 1." % value)
```