Python SSH

Hi.
I’m try to make a script to automate some tasks with Fortigate Fw.
When I try the connection , python sollevate this exception.

>>> ssh.connect("192.168.1.99",
	    22,
            username="admin", 
            password=None,
            look_for_keys=False )
Traceback (most recent call last):
  File "<pyshell#7>", line 1, in <module>
    ssh.connect("192.168.1.99",
  File "C:\...\Python38-32\lib\site-packages\paramiko\client.py", line 435, in connect
    self._auth(
  File "C:\...\Python38-32\lib\site-packages\paramiko\client.py", line 765, in _auth
    raise SSHException("No authentication methods available")
paramiko.ssh_exception.SSHException: No authentication methods available

I discovered that issue exist with no password for ‘admin’ user, for example if I set a password on the device, i have no error during the connection

The appliance has no password.

Thanks