public function index(string $indexName = null)
    {
        $this->indexName = $indexName ?? $this->tableName . '_' . $this->name . '_index';

        return $this;
    }
public function index(string $indexName = null)
    {
        $this->indexName = $indexName ?? $this->tableName . '_' . $this->name . '_index';

        return $this;
    }
public function index ( string $ indexName = null ) { $ this -> indexName = $ indexName ?? $ this -> tableName . '_' . $ this -> name . '_index' ; return $ this ; }
Defines an index for the column.

@param string|null $indexName Defaults to {column-name}_index

@return static
Defines an index for the column .