Adding Defect into Bulk Metal

Hi all,
I would like to generate an Interstitial Defect in my FCC metal.
I used analysis.defects.core.Interstitial to generate but not so sure what I should put into the second argument - defect site.

Do I need to have a specific coords position (for example, if I want to have an octahedral interstitial site) ?

Here is the example of my script
defect_gen = Interstitial(Bulk_fe_32,???)
defect_struct = defect_gen.generate_defect_structure()

Thank you all for your help!
Ngan Huynh

The Interstitial object holds the defect info. If you want to generate one you need to use one of the generators in