lib/Elastica/QueryBuilder/DSL/Aggregation.php
public function serial_diff(string $name, string $bucketsPath = null): SerialDiff
    {
        return new SerialDiff($name, $bucketsPath);
    }
public function serial_diff(string $name, string $bucketsPath = null): SerialDiff
    {
        return new SerialDiff($name, $bucketsPath);
    }
public function serial_diff ( string $ name , string $ bucketsPath = null ) : SerialDiff { return new SerialDiff ( $ name , $ bucketsPath ) ; }
serial diff aggregation.

@see https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-pipeline-serialdiff-aggregation.html

@param string      $name
@param string|null $bucketsPath

@return SerialDiff
serial diff aggregation .