from telethon.sync import TelegramClient
from telethon.sessions import StringSession
string = '1aaNk8EX-YRfwoRsebUkugFvht6DUPi_Q25UOCzOAqzc...'
with TelegramClient(StringSession(), api_id, api_hash) as client:
client.loop.run_until_complete(client.send_message('me', 'Hi'))