Augments an observation with debug info.

def augment_observation(
    observation, reward, cum_reward, frame_index, bar_color=None,
    header_height=27
):
  """Augments an observation with debug info."""
  img = PIL_Image().new(
      "RGB", (observation.shape[1], header_height,)
  )
  draw = PIL_ImageDraw().Draw(img)
  draw.text(
      (1, 0), "c:{:3}, r:{:3}".format(int(cum_reward), int(reward)),
      fill=(255, 0, 0)
  )
  draw.text(
      (1, 15), "f:{:3}".format(int(frame_index)),
      fill=(255, 0, 0)
  )
  header = np.copy(np.asarray(img))
  del img
  if bar_color is not None:
    header[0, :, :] = bar_color
  return np.concatenate([header, observation], axis=0)