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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 open(self):
 """Toggle state to open switch disconnector"""

        if self._state != 'open':
            if self._line is not None:
                self._state = 'open'
                self._nodes = self.grid.graph.nodes_from_line(self._line)
                self.grid.graph.remove_edge(
                    self._nodes[0], self._nodes[1])
            else:
                raise ValueError('``line`` is not set')