Remove a callback from the list

def unbind(self, callback):
        """Remove a callback from the list
        """
        handlers = self._handlers
        if handlers:
            filtered_callbacks = [f for f in handlers if f != callback]
            removed_count = len(handlers) - len(filtered_callbacks)
            if removed_count:
                self._handlers = filtered_callbacks
            return removed_count
        return 0