class Net::IMAP

def unselect

[RFC3691[https://tools.ietf.org/html/rfc3691]].
The server's capabilities must include +UNSELECT+

===== Capabilities

Related: #close

\\Deleted messages are not removed from the mailbox.
"_authenticated_" state. This is the same as #close, except that
to free the session resources for a mailbox and return to the
{[IMAP4rev2 §6.4.2]}[https://www.rfc-editor.org/rfc/rfc9051#section-6.4.2]
Sends an {UNSELECT command [RFC3691 §2]}[https://www.rfc-editor.org/rfc/rfc3691#section-3] 
def unselect
  send_command("UNSELECT")
end