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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 email(prompt=None, empty=False, mode="simple"):
 """Prompt an email address. This check is based on a simple regular expression and does not verify whether an email actually exists. Parameters prompt : str, optional Use an alternative prompt. empty : bool, optional Allow an empty response. mode : {'simple'}, optional 'simple' will use a simple regular expression. No other mode is implemented yet. Returns ------- str or None A str if the user entered a likely email address. None if the user pressed only Enter and ``empty`` was True. """

    if mode == "simple":
        s = _prompt_input(prompt)
        if empty and not s:
            return None
        else:
            if RE_EMAIL_SIMPLE.match(s):
                return s
            else:
                return email(prompt=prompt, empty=empty, mode=mode)
    else:
        raise ValueError