code: def get_series_first_release(self, series_id):
          
          df = self.get_series_all_releases(series_id)
          first_release = df.groupby('date').head(1)
          data = first_release.set_index('date')['value']
          return data
docs: Get first-release data for a Fred series id. This ignores any revision to the data series. For instance,
          The US GDP for Q1 2014 was first released to be 17149.6, and then later revised to 17101.3, and 17016.0.
          This will ignore revisions after the first release.
  
          Parameters
          ----------
          series_id : str
              Fred series id such as 'GDP'
  
          Returns
          -------
          data : Series
              a Series where each index is the observation date and the value is the data for the Fred series