text: import os
  import webbrowser
  def graphAST(self):
          
          dot = "digraph ASTTytus{ \n rankdir = TD\n node[shape = \"box\"]\n"
          dot += "S[label=\"S\"]\n"
          for node in self.nodes:
              dot += node.graphAST('','S')
          dot += "\n }"
          try:
              archivodot = open("ast.dot", "w")
              archivodot.write(dot)
              archivodot.close()
              cmd = 'dot \"' + 'ast.dot\" -o \"' +  "ast.pdf\" -Tpdf"
              print("Comando DOT : " + cmd)
              # os.system(cmd)
              # webbrowser.open_new_tab('ast.pdf')
              print(dot)
          except Exception as e:
              self.messagebox('Error reporte', str(e))