This operation outputs ref after the update is done.
This makes it easier to chain operations that need to use the reset value.
Unlike tf.math.subtract, this op does not broadcast. ref and value
must have the same shape.
A mutable Tensor. Must be one of the following types: float32,
float64, int64, int32, uint8, uint16, int16, int8,
complex64, complex128, qint8, quint8, qint32, half. Should be
from a Variable node.
A Tensor. Must have the same shape and dtype as ref. The value to
be subtracted to the variable.
An optional bool. Defaults to False. If True, the
subtraction will be protected by a lock; otherwise the behavior is
undefined, but may exhibit less contention.