说明：  信息源根据一个有限的或无限但可数的符号集生成一个任意符号序列也就是说，信源的输出是离散的随机变量。本实验要求编写计算图像的一阶二阶熵的程序
(Information sources based on a limited or unlimited number of symbols but can be set to generate a sequence of arbitrary symbols that is to say, the output source is the discrete random variable. Prepared in this experiment, the calculation of second-order image of the first order entropy of the process)