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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_edge(self, edge):
 """ Adds Edges to the probnet dict. Parameters edge: <Element Link at Links Node in XML> etree Element consisting Variable tag. Examples ------- """

        var1 = edge.findall('Variable')[0].attrib['name']
        var2 = edge.findall('Variable')[1].attrib['name']
        self.probnet['edges'][(var1, var2)] = {}
        self.probnet['edges'][(var1, var2)]['directed'] = edge.attrib['directed']
        # TODO: check for the case of undirected graphs if we need to add to both elements of the dic for a single edge.
        if edge.find('Comment') is not None:
            self.probnet['edges'][(var1, var2)]['Comment'] = edge.find('Comment').text
        if edge.find('Label') is not None:
            self.probnet['edges'][(var1, var2)]['Label'] = edge.find('Label').text
        if edge.find('AdditionalProperties/Property') is not None:
            self.probnet['edges'][(var1, var2)]['AdditionalProperties'] = {}
            for prop in edge.findall('AdditionalProperties/Property'):
                self.probnet['edges'][(var1, var2)]['AdditionalProperties'][prop.attrib['name']] = prop.attrib['value']