function contains( seen, searchValue ) {
	var i;
	for ( i = 0; i < seen.length; i++ ) {
		if ( seen[ i ] === searchValue ) {
			return true;
		}
	}
	return false;
}
Tests if the seen array contains a search value.

@private
@param {Array} seen - array of seen objects
@param {*} searchValue - search value
@returns {boolean} boolean indicating whether array contains search value