code: function uniqueTransducer(fn, xform) {
    const uniques = [];
  
    return {
      [p.init]() {
        return xform[p.init]();
      },
  
      [p.step](acc, input) {
        if (uniques.some(u => fn(input, u))) {
          return acc;
        }
        uniques.push(input);
        return xform[p.step](acc, input);
      },
  
      [p.result](value) {
        return xform[p.result](value);
      }
    };
  }
docs: A transducer function that is returned by the `{@link module:xduce.transducers.unique|unique}`,
  `{@link module:xduce.transducers.uniqueBy|uniqueBy}`, and
  `{@link module:xduce.transducers.uniqueWith|uniqueWith}` transducers.
  
  @private
  
  @param {function} fn The two-argument comparator function that defines when two values are equal.
  @param {module:xduce~transducerObject} xform The transducer object that the new one should be chained to.
  @return {module:xduce~transducerObject} A new transducer object chained to the provided transducer object.