_Map a(g);

 	  _Map a(g);

 	  // Constructor with a graph and a default value parameter

 	  // Constructor with a graph and a default value parameter

 	  _Map a2(g,t);

 	  _Map a2(g,t);

 	  // Copy constructor. Do we need it?

 	  // Copy constructor. Do we need it?

 	  _Map b=c;

 	  _Map b=c;

 	  ignore_unused_variable_warning(a2);

 	  ignore_unused_variable_warning(a2);

 	}

 	}

 	const _Map &c;

 	const _Map &c;