original_string: public function registerAlias($alias, $file, $extension = null)
      {
          if ($extension === null) {
              $extension = File::extension($file);
          }
  
          $extension = strtolower($extension);
  
          if (!isset($this->aliases[$extension])) {
              $this->aliases[$extension] = [];
          }
  
          $this->aliases[$extension][$alias] = $file;
  
          return $this;
      }
code: public function registerAlias($alias, $file, $extension = null)
      {
          if ($extension === null) {
              $extension = File::extension($file);
          }
  
          $extension = strtolower($extension);
  
          if (!isset($this->aliases[$extension])) {
              $this->aliases[$extension] = [];
          }
  
          $this->aliases[$extension][$alias] = $file;
  
          return $this;
      }
code_tokens: public function registerAlias ( $ alias , $ file , $ extension = null ) { if ( $ extension === null ) { $ extension = File :: extension ( $ file ) ; } $ extension = strtolower ( $ extension ) ; if ( ! isset ( $ this -> aliases [ $ extension ] ) ) { $ this -> aliases [ $ extension ] = [ ] ; } $ this -> aliases [ $ extension ] [ $ alias ] = $ file ; return $ this ; }
docstring: Register an alias to use for a longer file reference.
  @param string $alias Alias name. Eg: framework
  @param string $file Path to file to use for alias
  @param string $extension Extension name. Eg: css
  @return self
docstring_tokens: Register an alias to use for a longer file reference .