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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 time_to_first_byte(self):
 """ Time to first byte of the page request in ms """

        # The unknown page is just a placeholder for entries with no page ID.
        # As such, it would not have a TTFB
        if self.page_id == 'unknown':
            return None
        ttfb = 0
        for entry in self.entries:
            if entry['response']['status'] == 200:
                for k, v in iteritems(entry['timings']):
                    if k != 'receive':
                        if v > 0:
                            ttfb += v
                break
            else:
                ttfb += entry['time']

        return ttfb