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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _swap(vas, vas_location, vbs, vbs_location, l2v, vertices_resources, placements, machine):
 """Swap the positions of two sets of vertices. Parameters A set of vertices currently at vas_location. vas_location : (x, y) A set of vertices currently at vbs_location. vbs_location : (x, y) machine : :py:class:`rig.place_and_route.Machine` """

    # Get the lists of vertices at either location
    vas_location2v = l2v[vas_location]
    vbs_location2v = l2v[vbs_location]

    # Get the resource availability at either location
    vas_resources = machine[vas_location]
    vbs_resources = machine[vbs_location]

    # Move all the vertices in vas into vbs.
    for va in vas:
        # Update the placements
        placements[va] = vbs_location

        # Update the location-to-vertex lookup
        vas_location2v.remove(va)
        vbs_location2v.append(va)

        # Update the resource consumption after the move
        resources = vertices_resources[va]
        vas_resources = add_resources(vas_resources, resources)
        vbs_resources = subtract_resources(vbs_resources, resources)

    for vb in vbs:
        # Update the placements
        placements[vb] = vas_location

        # Update the location-to-vertex lookup
        vbs_location2v.remove(vb)
        vas_location2v.append(vb)

        # Update the resource consumption after the move
        resources = vertices_resources[vb]
        vas_resources = subtract_resources(vas_resources, resources)
        vbs_resources = add_resources(vbs_resources, resources)

    # Update the resources in the machine
    machine[vas_location] = vas_resources
    machine[vbs_location] = vbs_resources