Return the event position, if it exists.

        An event exist if:
        * end is < 0
        * event_type is matching
        Return -1 if the item is not found.

def __event_exist(self, event_type):
        """Return the event position, if it exists.

        An event exist if:
        * end is < 0
        * event_type is matching
        Return -1 if the item is not found.
        """
        for i in range(self.len()):
            if self.events_list[i][1] < 0 and self.events_list[i][3] == event_type:
                return i
        return -1