code: def get_chains(self):
          
          chains = []
          try:
              content = os.listdir(self._directory)
              for c in content:
                  if os.path.isdir(os.path.join(self._directory, c)) and c.startswith(
                          CHAIN_NAME[:-2]):
                      chains.append(c)
          except:
              pass
          chains.sort()
          return chains
docs: Return an ordered list of the `Chain_#` directories in the db
          directory.