public function clean(string $key = null): ConfigInterface
    {
        if (null !== $key) {
            unset($this->_config[$key]);
        } else {
            $this->_config = [];
        }

        return $this;
    }
public function clean(string $key = null): ConfigInterface
    {
        if (null !== $key) {
            unset($this->_config[$key]);
        } else {
            $this->_config = [];
        }

        return $this;
    }
public function clean ( string $ key = null ) : ConfigInterface { if ( null !== $ key ) { unset ( $ this -> _config [ $ key ] ) ; } else { $ this -> _config = [ ] ; } return $ this ; }
Remove single value or clean config

@param   string|null $key
@return  ConfigInterface
Remove single value or clean config