code: protected function joinMeta(Builder $query, $column)
      {
          $query->prefixColumnsForJoin();
  
          $alias = $this->generateMetaAlias();
  
          $table = (new Attribute)->getTable();
  
          $query->leftJoin("{$table} as {$alias}", function ($join) use ($alias, $column) {
              $join->on("{$alias}.metable_id", '=', $this->getQualifiedKeyName())
                  ->where("{$alias}.metable_type", '=', $this->getMorphClass())
                  ->where("{$alias}.meta_key", '=', $column);
          });
  
          return $alias;
      }
docs: Join meta attributes table.
  
  @param  \Sofa\Eloquence\Builder $query
  @param  string $column
  @return string