code: def validate_single_matching_uri(all_blockchain_uris: List[str], w3: Web3) -> str:
      
      matching_uris = [
          uri for uri in all_blockchain_uris if check_if_chain_matches_chain_uri(w3, uri)
      ]
  
      if not matching_uris:
          raise ValidationError("Package has no matching URIs on chain.")
      elif len(matching_uris) != 1:
          raise ValidationError(
              f"Package has too many ({len(matching_uris)}) matching URIs: {matching_uris}."
          )
      return matching_uris[0]
docs: Return a single block URI after validating that it is the *only* URI in
      all_blockchain_uris that matches the w3 instance.