def METHOD_NAME(self, dag):
    """Run the BasicSwap pass on `dag`.
    Args:
        dag (DAGCircuit): DAG to map.
    Returns:
        DAGCircuit: A mapped DAG.
    Raises:
        TranspilerError: if the coupling map or the layout are not
        compatible with the DAG, or if the coupling_map=None.
    """
    if self.fake_run:
        return self._fake_run(dag)
    new_dag = dag.copy_empty_like()
    if self.coupling_map is None:
        raise TranspilerError("BasicSwap cannot run with coupling_map=None")
    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")
    disjoint_utils.require_layout_isolated_to_component(
        dag, self.coupling_map if self.target is None else self.target
    )
    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:
                # Insert a new layer with the SWAP(s).
                swap_layer = DAGCircuit()
                swap_layer.add_qreg(canonical_register)
                path = self.coupling_map.shortest_undirected_path(physical_q0, physical_q1)
                for swap in range(len(path) - 2):
                    connected_wire_1 = path[swap]
                    connected_wire_2 = path[swap + 1]
                    qubit_1 = current_layout[connected_wire_1]
                    qubit_2 = current_layout[connected_wire_2]
                    # create the swap operation
                    swap_layer.apply_operation_back(
                        SwapGate(), qargs=[qubit_1, qubit_2], cargs=[]
                    )
                # layer insertion
                order = current_layout.reorder_bits(new_dag.qubits)
                new_dag.compose(swap_layer, qubits=order)
                # update current_layout
                for swap in range(len(path) - 2):
                    current_layout.swap(path[swap], path[swap + 1])
        order = current_layout.reorder_bits(new_dag.qubits)
        new_dag.compose(subdag, qubits=order)
    self.property_set["final_layout"] = current_layout
    return new_dag