Returns if the given signal is connected to the inputted slot.
        
        :param      signal | <variant>
                    slot   | <callable>
        
        :return     <bool> | is connected

def isConnected(self, signal, slot):
        """
        Returns if the given signal is connected to the inputted slot.
        
        :param      signal | <variant>
                    slot   | <callable>
        
        :return     <bool> | is connected
        """
        sig_calls = self._callbacks.get(signal, [])
        for callback in sig_calls:
            if callback == slot:
                return True
        return False