code: def _get_links(self,):
          
          res = ''
          if self.links:
              for l in self.links:
                  res += ' links = ' + str(l[0]) + '\n'
                  if l[0].child_nodes:
                      for chld in l[0].child_nodes:
                          res += '   child = ' + str(chld) + '\n'
                  if l[0].links:
                      for lnk in l[0].links:
                          res += '   sublink = ' + str(lnk[0]) + '\n'
          else:
              res += ' links = None\n'
              
          return res
docs: return the list of links of a node