At the API level,  FBO Accounts work the following way:
Subaccount-US
View API
import os
from synapse_pay_rest import Client
from synapse_pay_rest import User
from synapse_pay_rest.models.nodes import SubaccountUsNode
kwargs = {
'type': 'My Subaccount'
}
node = SubaccountUsNode.create(user, **kwargs)