'Some commands are strange... if you want to delay for 5 seconds you
need to set the value to 6; or 4... This value is added to the seconds:
>>> d = ExactDelay(\'sleep(%s)\')
>>> d.get_string_for_delay( 3 )
\'sleep(3)\'
>>> d.set_delay_delta( 1 )
>>> d.get_string_for_delay( 3 )
\'sleep(4)\''

def set_delay_delta(self, delta):

    self._delay_delta = delta
