Defined in tensorflow/python/ops/state_ops.py.
将 value 赋值给 ref，并输出 ref
Defined in tensorflow/python/framework/tensor_shape.py.
A mutable Tensor. Should be from a Variable node. May be uninitialized.
A Tensor. Must have the same type as ref. The value to be assigned to the variable.
An optional bool. Defaults to True. If true, the operation will validate that the shape of ‘value’ matches the shape of the Tensor being assigned to. If false, ‘ref’ will take on the shape of ‘value’.
An optional bool. Defaults to True. If True, the assignment will be protected by a lock; otherwise the behavior is undefined, but may exhibit less contention.
A name for the operation (optional).
Same as “ref”. Returned as a convenience for operations that want to use the new value after the variable has been reset.