code: function serializeList( elements, indent = INDENT, pad = 0, space ) {
     if( elements.length === 0 ) {
        return '';
     }
  
     const length = elements.reduce( ( sum, e ) => sum + e.length + 2, pad );
     const multiline = elements.some( element => /\n/.test( element ) );
     const compact = length < LIST_LENGTH && !multiline;
  
     const leader = compact ? ' ' : `\n${spaces( pad + indent, space )}`;
     const trailer = compact ? ' ' : `\n${spaces( pad, space )}`;
     const separator = `,${leader}`;
  
     const body = elements.join( separator );
  
     return `${leader}${body}${trailer}`;
  }
docs: Serialize the body of a list or object.
  @private
  @param {Array<String>} elements the serialized elements or key-value pairs
  @param {Number} [indent] the number of spaces to use for indent
  @param {Number} [pad] the initial left padding
  @param {String} [space] the character(s) to use for padding
  @return {String} the serialized JavaScript code