code: function ( from_path, to_path ) {
  
          if ( typeof from_path !== 'string' ) {
  
              throw { type: 'changeCSSRoot', message: 'First argument must be String' };
  
          }
  
          if ( typeof to_path !== 'string' ) {
  
              throw { type: 'changeCSSRoot', message: 'Second argument must be String' };
  
          }
  
          urls.filter( function ( value ) {
  
              return !/^(http|data|\/)/.test( _getURLValue( value ) );
  
          } ).forEach( function ( value ) {
  
              var url_path      = _getURLValue( value ),
                  absolute_path = path.join( from_path, url_path ),
                  new_path      = path.relative( to_path, absolute_path );
  
              _setURLValue( value, new_path );
  
          } );
  
      }
docs: Changes relative path of every relative url() address to the new base.
  
  @param  {string} from_path Old CSS folder.
  @param  {string} to_path   New CSS folder.