Create IP Address and attach to interface in Python

[llamafilm]

I'm trying to write a custom script that creates a new IP Address and attaches to an existing Interface. Testing in nbshell, I can't figure out the right syntax. I thought it should be like this:

>>> ipaddr = IPAddress(address='1.2.3.6', assigned_object_id=6516, assigned_object_type='dcim.interface')
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/opt/netbox-3.7.3/netbox/ipam/models/ip.py", line 794, in __init__
    super().__init__(*args, **kwargs)
  File "/opt/netbox-3.7.3/venv/lib/python3.11/site-packages/django/db/models/base.py", line 543, in __init__
    _setattr(self, field.name, rel_obj)
  File "/opt/netbox-3.7.3/venv/lib/python3.11/site-packages/django/db/models/fields/related_descriptors.py", line 266, in __set__
    raise ValueError(
ValueError: Cannot assign "'dcim.interface'": "IPAddress.assigned_object_type" must be a "ContentType" instance.

A similar POST to /api/ipam/ip-addresses/ works fine with this payload:

{
  "address": "1.2.3.6",
  "status": "active",
  "assigned_object_type": "dcim.interface",
  "assigned_object_id": 6516
}

I also tried assigned_object_type=Interface and that gave the same error. How is this supposed to be used?

[llamafilm]

I figured it out. For some reason the snapshot doesn't work, but that doesn't bother me much. the set() function happens immediately, without having to run save().

iface = Interface.objects.get(device_id=dev.id, name=data['primary_nic'].name)

ipaddr = IPAddress(address = data['primary_ip'])
ipaddr.full_clean()
ipaddr.save()

iface.snapshot()
iface.ip_addresses.set([ipaddr])