code: def previous_page(self):
          
          if not self.previous_page_url:
              return None
  
          response = self._version.domain.twilio.request('GET', self.previous_page_url)
          cls = type(self)
          return cls(self._version, response, self._solution)
docs: Return the `Page` before this one.
          :return Page: The previous page.