code: function( input, charset ) {
  
      if( /iso-?2022-?jp/i.test( charset ) ) {
        charset = 'shift_jis'
      }
  
      if( charset ) {
        return MIME.Iconv.decode( Buffer.from( input, 'base64' ), charset )
      } else {
        return Buffer.from( input, 'base64' ).toString()
      }
  
    }
docs: Decodes a base64 encoded string.
  
  @param  {String} input
  @param  {String} charset
  @return {String|Buffer}