message: Describe "learning_rate_power".
  Fixes
diff: @@ -52,6 +52,9 @@ class FtrlOptimizer(optimizer.Optimizer):
  Args:
  learning_rate: A float value or a constant float `Tensor`.
  learning_rate_power: A float value, must be less or equal to zero.
  + Controls how the learning rate decreases during training. Use zero for
  + a fixed learning rate. See section 3.1 in the
  + [paper](https://www.eecs.tufts.edu/~dsculley/papers/ad-click-prediction.pdf).
  initial_accumulator_value: The starting value for accumulators.
  Only zero or positive values are allowed.
  l1_regularization_strength: A float value, must be greater than or
  