docs: def l2_loss(tensor, weight=1.0, scope=None):
    """Define a L2Loss, useful for regularize, i.e. weight decay.
  
    Args:
      tensor: tensor to regularize.
      weight: an optional weight to modulate the loss.
      scope: Optional scope for name_scope.
  
    Returns:
      the L2 loss op.
    """
    with tf.name_scope(scope, 'L2Loss', [tensor]):
      weight = tf.convert_to_tensor(weight,
                                    dtype=tensor.dtype.base_dtype,
                                    name='loss_weight')
      loss = tf.multiply(weight, tf.nn.l2_loss(tensor), name='value')
      tf.add_to_collection(LOSSES_COLLECTION, loss)
      return loss