稀疏张量¶

Mars 支持稀疏张量，但目前只支持二维稀疏张量，未来将支持多维稀疏张量。

创建稀疏张量的函数¶

`mars.tensor.tensor`
`mars.tensor.zeros`	Return a new tensor of given shape and type, filled with zeros.
`mars.tensor.eye`	Return a 2-D tensor with ones on the diagonal and zeros elsewhere.
`mars.tensor.identity`	Return the identity tensor.
`mars.tensor.random.randint`	Return random integers from low (inclusive) to high (exclusive).

mars.tensor.trunc

mars.tensor.zeros