张量系列（tensor02）

张量的两种运算

1. 张量的乘（Tensor product）

tensorproduct()

2. 张量的缩并

tensorcontraction()

The matrix trace is equivalent to the contraction of a rank-2 array

Matrix product is equivalent to a tensor product of two rank-2 arrays, followed by a contraction of the 2nd and 3rd axes (in Python indexing axes number 1, 2).