original_string: public function clean(string $key = null): ConfigInterface
      {
          if (null !== $key) {
              unset($this->_config[$key]);
          } else {
              $this->_config = [];
          }
  
          return $this;
      }
code: public function clean(string $key = null): ConfigInterface
      {
          if (null !== $key) {
              unset($this->_config[$key]);
          } else {
              $this->_config = [];
          }
  
          return $this;
      }
code_tokens: public function clean ( string $ key = null ) : ConfigInterface { if ( null !== $ key ) { unset ( $ this -> _config [ $ key ] ) ; } else { $ this -> _config = [ ] ; } return $ this ; }
docstring: Remove single value or clean config
  
  @param   string|null $key
  @return  ConfigInterface
docstring_tokens: Remove single value or clean config