message: fix bug in maxout function
  The line "shape[axis] = -1" will make the shape wrong when dealing with batches with arbitrary sizes.
diff: @@ -3117,7 +3117,7 @@ def maxout(inputs, num_units, axis=-1, scope=None):
  raise ValueError('number of features({}) is not '
  'a multiple of num_units({})'.format(
  num_channels, num_units))
  - shape[axis] = -1
  + shape[axis] = num_units
  shape += [num_channels // num_units]
  # Dealing with batches with arbitrary sizes
  