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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _get_captcha(reddit_session, captcha_id):
 """Prompt user for captcha solution and return a prepared result."""

    url = urljoin(reddit_session.config['captcha'],
                  captcha_id + '.png')
    sys.stdout.write('Captcha URL: {0}\nCaptcha: '.format(url))
    sys.stdout.flush()
    raw = sys.stdin.readline()
    if not raw:  # stdin has reached the end of file
        # Trigger exception raising next time through. The request is
        # cached so this will not require and extra request and delay.
        sys.stdin.close()
        return None
    return {'iden': captcha_id, 'captcha': raw.strip()}