docs: def _visit(self, element, operation):
          """
          Visit and execute a operation in element and descendants.
  
          :param element: The element.
          :type element: hatemile.util.html.htmldomelement.HTMLDOMElement
          :param operation: The operation to be executed.
          :type operation: function
          """
  
          if self._is_valid_inherit_element(element):
              if element.has_children_elements():
                  children = element.get_children_elements()
                  for child in children:
                      self._visit(child, operation)
              elif self._is_valid_element(element):
                  operation(element)