code: def add_node(node, **kwds):
      
      nodes._add_node_class_names([node.__name__])
      for key, val in kwds.iteritems():
          try:
              visit, depart = val
          except ValueError:
              raise ValueError('Value for key %r must be a '
                                   '(visit, depart) function tuple' % key)
          if key == 'html':
              from docutils.writers.html4css1 import HTMLTranslator as translator
          elif key == 'latex':
              from docutils.writers.latex2e import LaTeXTranslator as translator
          else:
              # ignore invalid keys for compatibility
              continue
          setattr(translator, 'visit_'+node.__name__, visit)
          if depart:
              setattr(translator, 'depart_'+node.__name__, depart)
docs: add_node from Sphinx