/**
* Set the current field to the value if the document is inserted in an
* upsert operation.
*
* If an update operation with upsert: true results in an insert of a
* document, then $setOnInsert assigns the specified values to the fields in
* the document. If the update operation does not result in an insert,
* $setOnInsert does nothing.
*
* @see Expr::setOnInsert()
* @see https://docs.mongodb.org/manual/reference/operator/update/setOnInsert/
* @param mixed $value
* @return self
*/
public function setOnInsert($value)
{
$this->expr->setOnInsert($value);
return $this;
}