_makeCssText(styleObject) {
    const converterStack = [];

    forEach(styleObject, (value, key) => {
      if (['backgroundImage'].indexOf(key) > -1 && value !== 'none') {
        value = `url(${value})`;
      }

      converterStack.push(`${this._toUnderScore(key)}: ${value}`);
    });

    return converterStack.join(';');
  }
Style object to Csstext serialize
@param {object} styleObject - style object
@returns {string} - css text string
@private