message: Improves the documentation of control_dependencies.
diff: @@ -4489,6 +4489,22 @@ class Graph(object):
  return tf.matmul(tensor, tensor)
  ```
  + Also note that though execution of ops created under this scope will trigger
  + execution of the dependencies, the ops created under this scope might still
  + be pruned from a normal tensorflow graph. For example, in the following
  + snippet of code the dependencies are never executed:
  +
  + ```python
  + loss = model.loss()
  + with tf.control_dependencies(dependencies):
  + loss = loss + tf.constant(1) # note: dependencies ignored in the
  + # backward pass
  + return tf.gradients(loss, model.variables)
  + ```
  +
  + This is because evaluating the gradient graph does not require evaluating
  + the constant(1) op created in the forward pass.
  +
  Args:
  control_inputs: A list of `Operation` or `Tensor` objects which
  must be executed or computed before running the operations
  