message: Fix formatting in api_def_ApplyMomentum.pbtxt
  Keep summary limited to a sentence and move the partial sentence to description.
diff: @@ -52,9 +52,9 @@ var - lr * momentum * accum, so in the end, the var you get is actually
  var - lr * momentum * accum.
  END
  }
  - summary: "Update \'*var\' according to the momentum scheme. Set use_nesterov = True if you"
  + summary: "Update \'*var\' according to the momentum scheme."
  description: <<END
  -want to use Nesterov momentum.
  +Set use_nesterov = True if you want to use Nesterov momentum.
  accum = accum * momentum + grad
  var -= lr * accum
  