message: capitalize first word of each arg description
diff: @@ -914,8 +914,8 @@ def poisson(y_true, y_pred):
  ```
  Args:
  - y_true: tensor of true targets.
  - y_pred: tensor of predicted targets.
  + y_true: Tensor of true targets.
  + y_pred: Tensor of predicted targets.
  Returns:
  A `Tensor` with the mean Poisson loss.
  