message: Fix sqrt in lr formula.
diff: @@ -51,7 +51,7 @@ class AdamOptimizer(optimizer.Optimizer):
  described at the end of section2 of the paper:
  $$t := t + 1$$
  - $$lr_t := \text{learning\_rate} * \sqrt{(1 - beta_2^t) / (1 - beta_1^t)}$$
  + $$lr_t := \text{learning\_rate} * \sqrt{1 - beta_2^t} / (1 - beta_1^t)$$
  $$m_t := beta_1 * m_{t-1} + (1 - beta_1) * g$$
  $$v_t := beta_2 * v_{t-1} + (1 - beta_2) * g * g$$
  