code: function baseFindKey(collection, predicate, eachFunc) {
      var result;
      eachFunc(collection, function(value, key, collection) {
        if (predicate(value, key, collection)) {
          result = key;
          return false;
        }
      });
      return result;
    }
docs: The base implementation of methods like `_.findKey` and `_.findLastKey`,
  without support for iteratee shorthands, which iterates over `collection`
  using `eachFunc`.
  
  @private
  @param {Array|Object} collection The collection to inspect.
  @param {Function} predicate The function invoked per iteration.
  @param {Function} eachFunc The function to iterate over `collection`.
  @returns {*} Returns the found element or its key, else `undefined`.