(self, func)
Adds a callback to be invoked when the result arrives. The callback 
        function takes a single argument, which is the current AsyncResult
        (``self``). If the result has already arrived, the function is invoked
        immediately.
        
        :param func: the callback function to add
Adds a callback to be invoked when the result arrives. The callback 
        function takes a single argument, which is the current AsyncResult
        (``self``). If the result has already arrived, the function is invoked
        immediately.
        
        :param func: the callback function to add
Adds a callback to be invoked when the result arrives . The callback function takes a single argument which is the current AsyncResult ( self ) . If the result has already arrived the function is invoked immediately . : param func : the callback function to add
def add_callback(self, func):
        """Adds a callback to be invoked when the result arrives. The callback 
        function takes a single argument, which is the current AsyncResult
        (``self``). If the result has already arrived, the function is invoked
        immediately.
        
        :param func: the callback function to add
        """
        if self._is_ready:
            func(self)
        else:
            self._callbacks.append(func)
def add_callback ( self , func ) : if self . _is_ready : func ( self ) else : self . _callbacks . append ( func )