example code

import odoorpc  # Prepare the connection to the server
odoo = odoorpc.ODOO('localhost', port=8069)

# Check available databases
print(odoo.db.list())

# Login
odoo.login('db_name', 'user', 'passwd')

# Current user
user = odoo.env.user
print(user.name)            # name of the user connected
print(user.company_id.name) # the name of its company

# Simple 'raw' query
user_data = odoo.execute('res.users', 'read', [user.id])
print(user_data)

# Use all methods of a model
if 'sale.order' in odoo.env:
    Order = odoo.env['sale.order']
    order_ids = Order.search([])
    for order in Order.browse(order_ids):
        print(order.name)
        products = [line.product_id.name for line in order.order_line]
        print(products)

# Update data through a record
user.name = "Brian Jones"

I found the answer. Strangely enough they first give a lot of examples on this page but further down the page you will find the answer to this question: how to query the ir.model: https://www.odoo.com/documentation/12.0/webservices/odoo.html

When you create a new invoice in Odoo, it is in "Draft" state by default. Before you start coding, you should learn Odoo first: Odoo Documentation