docs: async def update_trend_data(self, startdate, enddate):
          """Update trends data json for specified time period."""
          url = '{}/users/{}/trends'.format(API_URL, self.userid)
          params = {
              'tz': self.device.tzone,
              'from': startdate,
              'to': enddate
              }
  
          trends = await self.device.api_get(url, params)
          if trends is None:
              _LOGGER.error('Unable to fetch eight trend data.')
          else:
              self.trends = trends['days']