def METHOD_NAME(self, position=None):
    """
    Find a given position on the playground, i.e. test if the
    given position is valid or invent a new one by creating a
    random one
    @param list optional coordinates on the playground or None for random
    @return list position or False if the given one was invalid
    """
    if position:
        if self.playground.isvalidposition(position):
            return position
        else:
            return False
    else:
        return self.playground.getrandomposition()