gistfile1.txt

    /**
     * Constructor                                                                                  
     * @param IContextSource $context IContextSource to inherit from                                
     */                                                                                             
    public function __construct( IContextSource $context ) {                                 
        if ( ! ( $context instanceof MutableContext ) ) {
          $context = $this->getMutableContextFromIContextSource( $context );
        }
    
        // Clone the original context object so we can change it without changing the               
        // source context one.                                                                      
        $context = clone $context;                                                                  
                                                                                                    
        // set this cloned context object as the context of this DerivativeContext instance,        
        // so any set*-call will be done on this one, like any get*-call                            
        $this->setContext( $context );                                                              
    }
    
    /**
     * @deprecated since 1.27 blah blah blah
     * @returns MutableContext
     */
    private function getMutableContextFromIContextSource( IContextSource $context ) {
    
    }