function map(children, func, context) {
	  var index = 0;

	  return _react2['default'].Children.map(children, function (child) {
	    if (!_react2['default'].isValidElement(child)) {
	      return child;
	    }

	    return func.call(context, child, index++);
	  });
	}
Count the number of "valid components" in the Children container.

@param {?*} children Children tree container.
@returns {number}