code: def _is_valid_heading(self):
          
  
          elements = self.parser.find('h1,h2,h3,h4,h5,h6').list_results()
          last_level = 0
          count_main_heading = 0
          self.validate_heading = True
          for element in elements:
              level = self._get_heading_level(element)
              if level == 1:
                  if count_main_heading == 1:
                      return False
                  else:
                      count_main_heading = 1
              if (level - last_level) > 1:
                  return False
              last_level = level
          return True
docs: Check that the headings of page are sintatic correct.
  
          :return: True if the headings of page are sintatic correct or False if
                   not.
          :rtype: bool