# Checking if the localization of an integral domain is integrally closed

I was playing around in Sage earlier today, and I can't seem to figure out how to check whether the localization of an order in a number field is integrally closed. I'm fairly new to Sage, so I'm a little confused as to what the issue is. My code is below:

```
K.<i> = NumberField(x^2 + 1)
O = K.order(2*i)
Op = O.localization(2 + 2*i)
Op.is_integrally_closed()
```

This gives me a `NotImplementedError`

saying that `IntegerModRing_generic_with_category`

object has no attribute `is_integrally_closed`

. I can see, however, that the object `Op`

has type `sage.rings.localization.Localization_with_category`

. I can't find the class `sage.rings.localization.Localization_with_category`

in the documentation, but in `sage.rings.localization`

, the base is listed as `sage.rings.ring.IntegralDomain`

, which has a method `is_integrally_closed()`

listed.

I know how to check the math here - I'm just trying to figure out how to get Sage to check this for me, and better understand how Sage categories, parents, classes, etc. work.

P.S. I am running Sage 9.5