code: def relu_density_logit(x, reduce_dims):
    
    frac = tf.reduce_mean(to_float(x > 0.0), reduce_dims)
    scaled = tf.log(frac + math.exp(-10)) - tf.log((1.0 - frac) + math.exp(-10))
    return scaled
docs: logit(density(x)).
  
    Useful for histograms.
  
    Args:
      x: a Tensor, typically the output of tf.relu
      reduce_dims: a list of dimensions
  
    Returns:
      a Tensor