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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 _who_when(self, s, cmd, section, accept_just_who=False):
 """Parse who and when information from a string. :return: a tuple of (name,email,timestamp,timezone). name may be the empty string if only an email address was given. """

        match = _WHO_AND_WHEN_RE.search(s)
        if match:
            datestr = match.group(3).lstrip()
            if self.date_parser is None:
                # auto-detect the date format
                if len(datestr.split(b' ')) == 2:
                    date_format = 'raw'
                elif datestr == b'now':
                    date_format = 'now'
                else:
                    date_format = 'rfc2822'
                self.date_parser = dates.DATE_PARSERS_BY_NAME[date_format]
            try:
                when = self.date_parser(datestr, self.lineno)
            except ValueError:
                print("failed to parse datestr '%s'" % (datestr,))
                raise
            name = match.group(1).rstrip()
            email = match.group(2)
        else:
            match = _WHO_RE.search(s)
            if accept_just_who and match:
                # HACK around missing time
                # TODO: output a warning here
                when = dates.DATE_PARSERS_BY_NAME['now']('now')
                name = match.group(1)
                email = match.group(2)
            elif self.strict:
                self.abort(errors.BadFormat, cmd, section, s)
            else:
                name = s
                email = None
                when = dates.DATE_PARSERS_BY_NAME['now']('now')
        if len(name) > 0:
            if name.endswith(b' '):
                name = name[:-1]
        # While it shouldn't happen, some datasets have email addresses
        # which contain unicode characters. See bug 338186. We sanitize
        # the data at this level just in case.
        if self.user_mapper:
            name, email = self.user_mapper.map_name_and_email(name, email)

        return Authorship(name, email, when[0], when[1])