:param significant_digits: int of the number of significant digits
            in the return
        :return: float of the time in seconds of how long the
             data took to stream

def stream_time(self, significant_digits=3):
        """
        :param significant_digits: int of the number of significant digits
            in the return
        :return: float of the time in seconds of how long the
             data took to stream
        """
        try:
            return round(
                self._timestamps['last_stream'] - self._timestamps['stream'],
                significant_digits)
        except Exception as e:
            return None