编写程序，输出如下所示图案。

def main():
    for i in range(1,5):
        for j in range(4-i):
            print(" ",end='')
        for j in range(1,2*i):
            print('*',end='')
        print('\n')
    for i in range(4,0,-1):
        for j in range(4-i):
            print(" ",end='')
        for j in range(1,2*i):
            print('*',end='')
        print('\n')
main()