def heartrate_time_series(start_date: nil, end_date: nil, period: nil)
      warn '[DEPRECATION] `heartrate_time_series` is deprecated.  Please use `hr_series_for_date_range` or `hr_series_for_period` instead.'

      regular_time_series_guard(
        start_date: start_date,
        end_date: end_date,
        period: period
      )

      second = period || format_date(end_date)

      url = ['user', user_id, 'activities/heart/date', format_date(start_date), second].join('/')

      get_call(url + '.json')
    end
def heartrate_time_series(start_date: nil, end_date: nil, period: nil)
      warn '[DEPRECATION] `heartrate_time_series` is deprecated.  Please use `hr_series_for_date_range` or `hr_series_for_period` instead.'

      regular_time_series_guard(
        start_date: start_date,
        end_date: end_date,
        period: period
      )

      second = period || format_date(end_date)

      url = ['user', user_id, 'activities/heart/date', format_date(start_date), second].join('/')

      get_call(url + '.json')
    end
retrieve heartrate time series