function _cbrtUnit(x) {
    if (x.value && type.isComplex(x.value)) {
      var result = x.clone();
      result.value = 1.0;
      result = result.pow(1.0 / 3); // Compute the units

      result.value = _cbrtComplex(x.value); // Compute the value

      return result;
    } else {
      var negate = isNegative(x.value);

      if (negate) {
        x.value = unaryMinus(x.value);
      } // TODO: create a helper function for this


      var third;

      if (type.isBigNumber(x.value)) {
        third = new type.BigNumber(1).div(3);
      } else if (type.isFraction(x.value)) {
        third = new type.Fraction(1, 3);
      } else {
        third = 1 / 3;
      }

      var _result = x.pow(third);

      if (negate) {
        _result.value = unaryMinus(_result.value);
      }

      return _result;
    }
  }
Calculate the cubic root for a Unit
@param {Unit} x
@return {Unit} Returns the cubic root of x
@private