设计一个程序，用后向Euler 法/梯形法求解电路系统的MNA 方程（该方程由stamp 程 序得到），其中线性方程的求解采用GCR 迭代法。-Design a program that uses the backward Euler method/trapezoid method for solving circuit system MNA equation (the equation obtained by the stamp program), in which the linear