例子：
a = 3
print np.squeeze(a) # 输出3
a = [3]
print np.squeeze(a) # 输出3
a = [[3]]
print np.squeeze(a) # 输出3
a = [3, 4]
print np.squeeze(a) # 输出[3, 4]
a = [[3, 4]]
print np.squeeze(a) # 输出[3, 4]
a = [[3, 4], 5]
print np.squeeze(a) # 输出[list([3, 4]) 5] 变得奇怪了
a = [[3, 4], [5]]
print np.squeeze(a) # 输出[list([3, 4]) list([5])]
