docs: function(source, ctx) {
    if (source.hasOwnProperty('format')) {
      if (validateFormats.hasOwnProperty(source.format)) {
        return validateFormats[source.format](source, ctx);
      } else {
        throw new Error('invalid format for textblock: ' + source.format);
      }
    }
    throw new Error('invalid format for textblock (did you pass an Object in?)');
  }