code: def get_previous_release(self):
          
          releases = self.get_releases()
          if not releases:
              return None
  
          current = self.get_current_release()
          if not current:
              return None
  
          try:
              current_idx = releases.index(current)
          except ValueError:
              return None
  
          try:
              return releases[current_idx + 1]
          except IndexError:
              return None
docs: Get the release ID of the deployment immediately
          before the "current" deployment, ``None`` if no previous
          release could be determined.
  
          This method performs two network operations.
  
          :return: The release ID of the release previous to the
              "current" release.
          :rtype: str