Connect ``slot`` to this singal.

        Args:
            slot (callable): Callable object wich accepts keyword arguments.

        Raises:
            InvalidSlot: If ``slot`` doesn't accept keyword arguments.

def connect(self, slot):
        """Connect ``slot`` to this singal.

        Args:
            slot (callable): Callable object wich accepts keyword arguments.

        Raises:
            InvalidSlot: If ``slot`` doesn't accept keyword arguments.
        """
        self._ensure_slot_args(slot)
        if not self.is_connected(slot):
            self.slots.append(slot)