continue
		}
		tokens = append(tokens, substitution...)
	}
	in.Push(NewSlice(in.Base(), in.Line(), tokens))
}

// argsFor returns a map from formal name to actual value for this argumented macro invocation.
// The opening parenthesis has been absorbed.
func (in *Input) argsFor(macro *Macro) map[string][]Token {
	var args [][]Token
	// One macro argument per iteration. Collect them all and check counts afterwards.

    *   Add meta-distribution BatchReshape which reshapes batch dimensions.
    *   `tf.contrib.layers.recompute_grad` works for explicit gradient
        checkpointing on TPU.
    *   Add `tf.contrib.framework.argsort`.
    *   Allow `DNNBoostedTreeCombinedEstimator` to work with core versions of
        feature columns and losses.
    *   Add non-linear image warping ops: `tf.contrib.image.sparse_image_warp`,