Groovy script to filter entities by ICP_Entity_Yes

We are using a groovy script within a form. We have it currently building the rows with ILvl0Descendants of the entity in the user's POV. This works with no problem. Now we'd like to narrow that list to just level 0s that are flagged as intercompany entities: ICP_Entity_Yes. We can get to this parameter if we were manually building the form with Variables - Attributes - Intercompany Entity - ICP_Entity_Yes, but are not sure how to accomplish this in our groovy script. Searched through the groovy documentation, but couldn't find something that would help.