code: function filterTransducer(fn, xform) {
    return {
      [p.init]() {
        return xform[p.init]();
      },
  
      [p.step](acc, input) {
        return fn(input) ? xform[p.step](acc, input) : acc;
      },
  
      [p.result](value) {
        return xform[p.result](value);
      }
    };
  }
docs: A transducer function that is returned by the `{@link module:xduce.transducers.filter|filter}`,
  `{@link module:xduce.transducers.reject|reject}`, and `{@link module:xduce.transducers.compact|compact}` transducers.
  
  @private
  
  @param {function} fn A single-parameter predicate function that determines which elements should be retained in the
  output collection.
  @param {module:xduce~transducerObject} xform The transducer object that the new one should be chained to.
  @return {module:xduce~transducerObject} A new transducer object, performing no transformation and chaining to the
  provided transducer object.