def METHOD_NAME(self, dag):
    """Do a fake run the BasicSwap pass on `dag`.
    Args:
        dag (DAGCircuit): DAG to improve initial layout.
    Returns:
        DAGCircuit: The same DAG.
    Raises:
        TranspilerError: if the coupling map or the layout are not
        compatible with the DAG.
    """
    if len(dag.qregs) != 1 or dag.qregs.get("q", None) is None:
        raise TranspilerError("Basic swap runs on physical circuits only")
    if len(dag.qubits) > len(self.coupling_map.physical_qubits):
        raise TranspilerError("The layout does not match the amount of qubits in the DAG")
    canonical_register = dag.qregs["q"]
    trivial_layout = Layout.generate_trivial_layout(canonical_register)
    current_layout = trivial_layout.copy()
    for layer in dag.serial_layers():
        subdag = layer["graph"]
        for gate in subdag.two_qubit_ops():
            physical_q0 = current_layout[gate.qargs[0]]
            physical_q1 = current_layout[gate.qargs[1]]
            if self.coupling_map.distance(physical_q0, physical_q1) != 1:
                path = self.coupling_map.shortest_undirected_path(physical_q0, physical_q1)
                # update current_layout
                for swap in range(len(path) - 2):
                    current_layout.swap(path[swap], path[swap + 1])
    self.property_set["final_layout"] = current_layout
    return dag