(self, node)
return temp_node
find the minimum node when node regard as a root node
        :param node:
        :return: minimum node
find the minimum node when node regard as a root node
        :param node:
        :return: minimum node
find the minimum node when node regard as a root node : param node : : return : minimum node
def minimum(self, node):
        """
        find the minimum node when node regard as a root node
        :param node:
        :return: minimum node
        """
        temp_node = node
        while temp_node.left:
            temp_node = temp_node.left
        return temp_node
def minimum ( self , node ) : temp_node = node while temp_node . left : temp_node = temp_node . left return temp_node