Some people find it easier to understand the API calls by turning on logging so they can see, in real-time, what Odoo is doing as it creates and processes different kinds of documents.

https://www.odoo.com/documentation/13.0/reference/cmdline.html#logging

All I have is a script written in Python for version 12.0, we made major changes to the Accounting framework and account.invoice and account.invoice.line no longer exist.  You should be able to adapt this to work with account.move and account.move.line instead:

Switch the calls based on the examples at

import xmlrpclib
import csv
import requests
import base64
from dateutil.parser import parse
from time import gmtime, strftime


username = ''
pwd = ''
dbname = ''

sock_common = xmlrpclib.ServerProxy ('http://server:8069/xmlrpc/common', allow_none=True)

uid = sock_common.login(dbname, username, pwd)

sock = xmlrpclib.ServerProxy('http://server:8069/xmlrpc/2/object', allow_none=True)


reader = csv.reader(open('/opt/imports/vendor_bills.csv','rb'))

count = 0
for row in reader:
    if count == 0:
        count+=1
        continue
    count += 1

    invoice_id = False
    invoice_exist = False
    partner_id = sock.execute(dbname, uid, pwd, 'res.partner', 'search', [('ref', '=', row[0]),('company_id', '=', 1)])
    partner_id = partner_id[0]

    if float(row[7]) > 0:
        invoice_type  = 'in_invoice'
        price_unit = row[7]
    else:
        invoice_type = 'in_refund'
        price_unit = -float(row[7])

    currency = sock.execute(dbname, uid, pwd, 'res.currency', 'search', [('name', '=', 'USD')])
    journal = sock.execute(dbname, uid, pwd, 'account.journal', 'search', [('name', '=', 'Vendor Bills'),('company_id', '=', 1)])
    invoice_vals = {
		'move_name': row[2],
		'name': row[2],
		'type': invoice_type,
		'company_id': 1,
		'date_invoice': parse(row[3]).strftime("%Y-%m-%d"),
		'date_due': parse(row[5]).strftime("%Y-%m-%d"),
		'partner_id': partner_id,
		'currency_id': currency and currency[0],
		'journal_id': journal and journal[0] or False,
        'x_migrated':True,
		'origin': 'Imported AP',
        'user_id': False,
		}

    invoice_id = sock.execute(dbname, uid,pwd, 'account.invoice','create',invoice_vals)
    account_id = sock.execute(dbname, uid, pwd, 'account.account', 'search', [('name', '=', 'Open AP'),('company_id', '=', 1)])
    invoice_line_vals = {
			'quantity': 1,
			'price_unit': price_unit,
			'account_id': account_id and account_id[0],
			'company_id':1,
			'name': 'Open AP',
			'invoice_id': invoice_id,
			'partner_id': partner_id,
			}
    sock.execute(dbname, uid,pwd, 'account.invoice.line','create',invoice_line_vals)
    sock.execute_kw(dbname, uid, pwd, 'account.invoice', 'action_invoice_open', [invoice_id])

I know that the action_invoice_open function is executed intermittently and the self is passed to the function, but I don't know how to do that using the XMLRPC library, any example works, apart from the LOG I have everything activated as the link you shared tells me