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define(['./_baseFlatten', './_baseIteratee', './_baseRest', './_baseUniq', './isArrayLikeObject', './last'], function(baseFlatten, baseIteratee, baseRest, baseUniq, isArrayLikeObject, last) {
  /** Used as a safe reference for `undefined` in pre-ES5 environments. */  var undefined;
  /**   * This method is like `_.union` except that it accepts `iteratee` which is   * invoked for each element of each `arrays` to generate the criterion by   * which uniqueness is computed. Result values are chosen from the first   * array in which the value occurs. The iteratee is invoked with one argument:   * (value).   *   * @static   * @memberOf _   * @since 4.0.0   * @category Array   * @param {...Array} [arrays] The arrays to inspect.   * @param {Function} [iteratee=_.identity] The iteratee invoked per element.   * @returns {Array} Returns the new array of combined values.   * @example   *   * _.unionBy([2.1], [1.2, 2.3], Math.floor);   * // => [2.1, 1.2]   *   * // The `_.property` iteratee shorthand.   * _.unionBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');   * // => [{ 'x': 1 }, { 'x': 2 }]   */  var unionBy = baseRest(function(arrays) {    var iteratee = last(arrays);    if (isArrayLikeObject(iteratee)) {      iteratee = undefined;    }    return baseUniq(baseFlatten(arrays, 1, isArrayLikeObject, true), baseIteratee(iteratee, 2));  });
  return unionBy;});