protected function getEntityHashesFromRelation(string $relation): array
    {
        return array_map(function (Aggregate $aggregate) {
            return $aggregate->getEntityHash();
        }, $this->relationships[$relation]);
    }
protected function getEntityHashesFromRelation(string $relation): array
    {
        return array_map(function (Aggregate $aggregate) {
            return $aggregate->getEntityHash();
        }, $this->relationships[$relation]);
    }
protected function getEntityHashesFromRelation ( string $ relation ) : array { return array_map ( function ( Aggregate $ aggregate ) { return $ aggregate -> getEntityHash ( ) ; } , $ this -> relationships [ $ relation ] ) ; }
Return an array of Entity Hashes from a specific relation.

@param string $relation

@return array
Return an array of Entity Hashes from a specific relation .