'Close the active connection to the device'

def close(self):

    display.display('closing    ssh    connection    to    device', log_only=True)
    if self._shell:
        display.display('firing    event:    on_close_shell()', log_only=True)
        self._terminal.on_close_shell()
        self._shell.close()
        self._shell = None
        display.display('cli    session    is    now    closed', log_only=True)
    super(Connection, self).close()
    self._connected = False
    display.display('ssh    connection    has    been    closed    successfully', log_only=True)
