How can I obtain the partyId when updating inventory?

I want to update inventory using submit_inventory_update(https://python-amazon-sp-api.readthedocs.io/en/latest/endpoints/vendor_direct_fulfillment_inventory.html). How can I get the partyId in my vendor account?

<img width="1011" alt="image" src="https://github.com/saleweaver/python-amazon-sp-api/assets/80157042/f292269b-6caa-4c00-84c3-8460eaf0b560">
