/**
* Counts and returns the total the number of items in an array.
*
* The argument can be any expression as long as it resolves to an array.
*
* @see http://docs.mongodb.org/manual/reference/operator/aggregation/size/
* @see Expr::size
* @param mixed|Expr $expression
* @return self
*/
public function size($expression)
{
$this->expr->size($expression);
return $this;
}
