code: function toHiragana(input = '', options = {}) {
    const config = Object.assign({}, DEFAULT_OPTIONS, options);
    if (config.passRomaji) return katakanaToHiragana(input);
    if (isRomaji(input)) return romajiToHiragana(input, config);
    if (isMixed(input, { passKanji: true })) {
      const romaji = katakanaToHiragana(input);
      return romajiToHiragana(romaji, config);
    }
    return katakanaToHiragana(input);
  }
docs: Convert input to [Hiragana](https://en.wikipedia.org/wiki/Hiragana)
  @param  {String} [input=''] text
  @param  {DefaultOptions} [options=defaultOptions]
  @return {String} converted text
  @example
  toHiragana('toukyou, オオサカ')
  // => 'とうきょう、　おおさか'
  toHiragana('only カナ', { passRomaji: true })
  // => 'only かな'
  toHiragana('wi')
  // => 'うぃ'
  toHiragana('wi', { useObsoleteKana: true })
  // => 'ゐ'