'Finds the current network device prompt, last line only.'

def find_prompt(self, delay_factor=1):

    delay_factor = self.select_delay_factor(delay_factor)
    self.clear_buffer()
    self.write_channel(u'\n')
    time.sleep((delay_factor * 0.1))
    prompt = self.read_channel()
    if self.ansi_escape_codes:
        prompt = self.strip_ansi_escape_codes(prompt)
    log.debug(u'prompt1:    {0}'.format(prompt))
    count = 0
    prompt = prompt.strip()
    while ((count <= 10) and (not prompt)):
        prompt = self.read_channel().strip()
        if prompt:
            log.debug(u'prompt2a    repr:    {0}'.format(repr(prompt)))
            log.debug(u'prompt2b:    {0}'.format(prompt))
            if self.ansi_escape_codes:
                prompt = self.strip_ansi_escape_codes(prompt).strip()
        else:
            self.write_channel(u'\n')
            time.sleep((delay_factor * 0.1))
        count += 1
    log.debug(u'prompt3:    {0}'.format(prompt))
    prompt = self.normalize_linefeeds(prompt)
    prompt = prompt.split(u'\n')[(-1)]
    prompt = prompt.strip()
    if (not prompt):
        raise ValueError(u'Unable    to    find    prompt:    {}'.format(prompt))
    time.sleep((delay_factor * 0.1))
    self.clear_buffer()
    return prompt
