code: def convert_rgb_to_symmetric_real(x):
    
    with tf.name_scope("rgb_to_real", values=[x]):
      x = to_float(x)
      # Convert each pixel intensity in [0, 1, 2, ..., 255] into a real number in
      # the range [-1, 1].
      x = (x / 127.5) - 1
      return x
docs: Conversion of pixel values to real numbers.