_toTex (options) {
      if ((!options) ||
          (options && !options.parenthesis) ||
          (options && options.parenthesis === 'keep')) {
        return `\\left(${this.content.toTex(options)}\\right)`
      }
      return this.content.toTex(options)
    }
Get LaTeX representation
@param {Object} options
@return {string} str
@override