function formatAPI(nameOrFormatMap, callback) {
      if (typeof nameOrFormatMap === 'undefined') {
          return registry.list();
      }
      else if (typeof nameOrFormatMap === 'string') {
          if (typeof callback === 'function') {
              registry.register(nameOrFormatMap, callback);
          }
          else {
              return registry.get(nameOrFormatMap);
          }
      }
      else {
          registry.registerMany(nameOrFormatMap);
      }
  }
Custom format API

@see https://github.com/json-schema-faker/json-schema-faker#custom-formats
@param nameOrFormatMap
@param callback
@returns {any}