function getIteratorFn(maybeIterable) {
	  var iteratorFn = maybeIterable && (ITERATOR_SYMBOL && maybeIterable[ITERATOR_SYMBOL] || maybeIterable[FAUX_ITERATOR_SYMBOL]);
	  if (typeof iteratorFn === 'function') {
	    return iteratorFn;
	  }
	}
Returns the iterator method function contained on the iterable object.

Be sure to invoke the function with the iterable as context:

    var iteratorFn = getIteratorFn(myIterable);
    if (iteratorFn) {
      var iterator = iteratorFn.call(myIterable);
      ...
    }

@param {?object} maybeIterable
@return {?function}