def to_sexp(indent=0)
      indented = "  " * indent
      sexp = "#{indented}(#{fancy_type}"

      children.each do |child|
        if child.is_a?(Node)
          sexp += "\n#{child.to_sexp(indent + 1)}"
        else
          sexp += " #{child.inspect}"
        end
      end

      sexp += ")"

      sexp
    end
def to_sexp(indent=0)
      indented = "  " * indent
      sexp = "#{indented}(#{fancy_type}"

      children.each do |child|
        if child.is_a?(Node)
          sexp += "\n#{child.to_sexp(indent + 1)}"
        else
          sexp += " #{child.inspect}"
        end
      end

      sexp += ")"

      sexp
    end
Converts `self` to a pretty-printed s-expression.

 @param  [Integer] indent Base indentation level.
 @return [String]