function wrapperToIterator() {
      return this;
    }
Enables the wrapper to be iterable.

@name Symbol.iterator
@memberOf _
@since 4.0.0
@category Seq
@returns {Object} Returns the wrapper object.
@example

var wrapped = _([1, 2]);

wrapped[Symbol.iterator]() === wrapped;
// => true

Array.from(wrapped);
// => [1, 2]