How to access Remote Server using SFTP in Python?

I am trying to access storage on a remote server from a remote Linux machine within jupyter notebook using pysftp But I am getting an error "No Hostkey for host found"

Can anyone suggest solution or a better alternative?

I was trying this code

import pysftp

with pysftp.Connection(host = Hostname, username= username, password= password) as sftp:
    print("Connection Successful")
    

Error SSHException: No hostkey for host ****** found.