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	\begin{pgfonlayer}{nodelayer}
		\node [style=none] (0) at (-3, 0) {};
		\node [style=none] (1) at (-3, -1) {};
		\node [style=none] (2) at (-2, -1) {};
		\node [style=none] (3) at (-2, 0) {};
		\node [style=none] (4) at (-1, -1) {};
		\node [style=none] (5) at (-1, 0) {};
		\node [style=none] (6) at (0, 0) {};
		\node [style=none] (8) at (-1, 1) {};
		\node [style=none] (9) at (0, 1) {};
		\node [style=none] (10) at (1, 1) {};
		\node [style=none] (11) at (1, 0) {};
		\node [style=none] (12) at (2, 1) {};
		\node [style=none] (13) at (1, 2) {};
		\node [style=none] (14) at (2, 2) {};
		\node [style=none] (15) at (2, 0) {};
		\node [style=none] (16) at (-2, 1) {};
	\end{pgfonlayer}
	\begin{pgfonlayer}{edgelayer}
		\draw (0.center) to (3.center);
		\draw (3.center) to (5.center);
		\draw [style=blue-double] (0.center) to (1.center);
		\draw (1.center) to (2.center);
		\draw (2.center) to (3.center);
		\draw (2.center) to (4.center);
		\draw (4.center) to (5.center);
		\draw [style=extend-edge] (6.center) to (5.center);
		\draw (5.center) to (8.center);
		\draw [style=extend-edge] (8.center) to (9.center);
		\draw (9.center) to (6.center);
		\draw (11.center) to (15.center);
		\draw (15.center) to (12.center);
		\draw (12.center) to (10.center);
		\draw (11.center) to (10.center);
		\draw (10.center) to (13.center);
		\draw [style=blue-double] (13.center) to (14.center);
		\draw (14.center) to (12.center);
		\draw (16.center) to (8.center);
		\draw (16.center) to (3.center);
		\draw (9.center) to (10.center);
		\draw (11.center) to (6.center);
	\end{pgfonlayer}
\end{tikzpicture}
