code: function write(config, filePath) {
      switch (path.extname(filePath)) {
          case ".js":
              writeJSConfigFile(config, filePath);
              break;
  
          case ".json":
              writeJSONConfigFile(config, filePath);
              break;
  
          case ".yaml":
          case ".yml":
              writeYAMLConfigFile(config, filePath);
              break;
  
          default:
              throw new Error("Can't write to unknown file type.");
      }
  }
docs: Writes a configuration file.
  @param {Object} config The configuration object to write.
  @param {string} filePath The filename to write to.
  @returns {void}
  @throws {Error} When an unknown file type is specified.
  @private