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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_node(node, **kwds):
 """add_node from Sphinx """

    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)