code: function looksLikeFraction (value) {
    return (value &&
        typeof value === 'object' &&
        typeof value.s === 'number' &&
        typeof value.n === 'number' &&
        typeof value.d === 'number') || false
  }
docs: Check whether a value looks like a Fraction (unsafe duck-type check)
  @param {*} value
  @return {boolean}