def run(self, dag):
        """
        Pick a convenient layout depending on the best matching
        qubit connectivity, and set the property `layout`.

        Args:
            dag (DAGCircuit): DAG to find layout for.

        Raises:
            TranspilerError: if dag wider than self.coupling_map
        """
        num_dag_qubits = sum([qreg.size for qreg in dag.qregs.values()])
        if num_dag_qubits > self.coupling_map.size():
            raise TranspilerError('Number of qubits greater than device.')
        best_sub = self._best_subset(num_dag_qubits)
        layout = Layout()
        map_iter = 0
        for qreg in dag.qregs.values():
            for i in range(qreg.size):
                layout[(qreg, i)] = int(best_sub[map_iter])
                map_iter += 1
        self.property_set['layout'] = layout
Pick a convenient layout depending on the best matching
        qubit connectivity, and set the property `layout`.

        Args:
            dag (DAGCircuit): DAG to find layout for.

        Raises:
            TranspilerError: if dag wider than self.coupling_map