public function delete_index(string $table, string $key): bool
  {
    return $this->language->delete_index($table, $key);
  }
public function delete_index(string $table, string $key): bool
  {
    return $this->language->delete_index($table, $key);
  }
public function delete_index ( string $ table , string $ key ) : bool { return $ this -> language -> delete_index ( $ table , $ key ) ; }
Deletes index on a column of the table.

@todo far vedere a thomas perchè non funziona/return data

```php
\bbn\x::dump($db->delete_db_index('table_users','id_group'));
// (void)
```

@param string $table The table's name.
@param string $key The key's name.
@return bool
Deletes index on a column of the table .