code: def _get_source_snapshots(self, snapshot, fallback_self=False):
          
          if not snapshot:
              return []
  
          source_snapshots = re.findall(r"'([\w\d\.-]+)'", snapshot['Description'])
          if not source_snapshots and fallback_self:
              source_snapshots = [snapshot['Name']]
  
          source_snapshots.sort()
          return source_snapshots
docs: Get list of source snapshot names of given snapshot
  
          TODO: we have to decide by description at the moment