func NewIndentWriter(w io.Writer) *IndentWriter {
	return &IndentWriter{writer: w}
}
NewIndentWriter returns a new pointer to IndentWriter that will write using
the given io.Writer.
package ast
import (
	"fmt"
	"io"
)
type IndentWriter struct {
	writer io.Writer
	depth  int
}
var _ HWriter = (*IndentWriter)(nil)