# Error: 'Object has no attribute 'intersection''

Hi, I am pretty new to SAGE and and am not understanding why my code keeps giving me the error **'RelativeOrder_with_category' object has no attribute 'intersection'**. Here is my code:

```
sage: P1=x^3-x^2-4*x-1
sage: P2=x^3+x^2-2*x-1
sage: K1.<p>=NumberField(P1)
sage: K2.<d>=NumberField(P2)
sage: K.<p,d>=ExtensionField(K1,P2)
sage: O_K=K.ring_of_integers()
sage: A_K1=O_K.intersection(K1)
AttributeError: 'RelativeOrder_with_category' object has no attribute 'intersection'
```

I have looked at a lot of examples from other questions, but I can't seem to find a solution.

I cannot reproduce your issue with SageMath 8.3 since the step

`K.<p,d>=ExtensionField(K1,P2)`

leads toWhich version of SageMath are you using?

AFAICT there is no class or factory in any version of Sage called just

`ExtensionField`

, so it's either user-defined, or a rename of something else built into Sage. It would help to know exactly what that is. That said, it seems you have there a`RelativeOrder`

which, according to the docs, is the class used for orders in "some relative number field". I don't know what is meant by "relative" in terms of number fields but I'm not an algebra expert. But it seems that`RelativeOrder`

does not have an`intersection()`

method (perhaps it doesn't make sense for it to). However,`RelativeOrder`

does appear to have an "absolute" order which it is defined relativeto. So maybe what you want is`O_K.absolute_order().intersection(K1)`

.