private static TomlParseResult readToml(final String filepath) throws Exception {
    TomlParseResult toml;

    try {
      toml = TomlConfigFileParser.loadConfigurationFromFile(filepath);
    } catch (Exception e) {
      throw new Exception(
          "Unable to read permissioning TOML config file : " + filepath + " " + e.getMessage());
    }
    return toml;
  }
This method retrieves an array from parsed toml, using the given key.

@param tomlParseResult result of a prior toml parse
@param key key to fetch
@return The array matching the key if it exists, or null.
ethereum/permissioning/src/main/java/org/hyperledger/besu/ethereum/permissioning/PermissioningConfigurationBuilder.java