How to use the pygmsh.built_in.surface_base.SurfaceBase function in pygmsh

# From :
        #
        # > In this last extrusion command we retrieved the volume number
        # > programatically by saving the output of the command into a
        # > list. This list will contain the "top" of the extruded surface (in
        # > out[0]) as well as the newly created volume (in out[1]).
        #
        top = f"{name}[0]"
        extruded = f"{name}[1]"

        if isinstance(input_entity, LineBase):
            top = LineBase(top)
            # A surface extruded from a single line has always 4 edges
            extruded = SurfaceBase(extruded, 4)
        elif isinstance(input_entity, (SurfaceBase, self.Polygon)):
            top = SurfaceBase(top, input_entity.num_edges)
            extruded = VolumeBase(extruded)
        elif isinstance(input_entity, PointBase):
            top = PointBase(top)
            extruded = LineBase(extruded)
        else:
            top = Dummy(top)
            extruded = Dummy(extruded)

        lat = []
        # lateral surfaces can be deduced only if we start from a SurfaceBase
        # or a Polygon
        if isinstance(input_entity, (SurfaceBase, self.Polygon)):
            # out[0]` is the surface, out[1] the top, and everything after that
            # the sides, cf.
            # . Each
            # lateral surface has 4 edges: the one from input_entity, the one

self._GMSH_CODE.append(extrusion_string)

        # From :
        #
        # > In this last extrusion command we retrieved the volume number
        # > programatically by saving the output of the command into a
        # > list. This list will contain the "top" of the extruded surface (in
        # > out[0]) as well as the newly created volume (in out[1]).
        #
        top = f"{name}[0]"
        extruded = f"{name}[1]"

        if isinstance(input_entity, LineBase):
            top = LineBase(top)
            # A surface extruded from a single line has always 4 edges
            extruded = SurfaceBase(extruded, 4)
        elif isinstance(input_entity, (SurfaceBase, self.Polygon)):
            top = SurfaceBase(top, input_entity.num_edges)
            extruded = VolumeBase(extruded)
        elif isinstance(input_entity, PointBase):
            top = PointBase(top)
            extruded = LineBase(extruded)
        else:
            top = Dummy(top)
            extruded = Dummy(extruded)

        lat = []
        # lateral surfaces can be deduced only if we start from a SurfaceBase
        # or a Polygon
        if isinstance(input_entity, (SurfaceBase, self.Polygon)):
            # out[0]` is the surface, out[1] the top, and everything after that
            # the sides, cf.

from .surface_base import SurfaceBase


class CompoundSurface(SurfaceBase):
    """
    Generates the Compound Surface Gmsh function.
    Creates a compound surface from several elementary surfaces.
    When meshed, a compound surface will be reparametrized as
    a single surface, whose mesh can thus cross internal boundaries.
    Compound surfaces are mostly useful for remeshing discrete models.

    Parameters
    ----------
    surfaces : array-like[N]
        Contains the identification number of the elementary surfaces
        that should be reparametrized as a single surface.
    """

    def __init__(self, surfaces):
        super().__init__()

from .. import built_in


class SurfaceBase(built_in.surface_base.SurfaceBase):
    """
    Increments the Surface ID every time a new surface object
    is created. Inherits from built_in SurfaceBase.
    """

    _ID = 0
    dimension = 2

    def __init__(self, is_list=False, id0=None):
        super().__init__(id0=id0)

        self.is_list = is_list
        if is_list:
            self.id += "[]"
        return

if not isinstance(entities, list):
            entities = [entities]

        d = {0: "Point", 1: "Line", 2: "Surface", 3: "Volume"}
        tpe = d[entities[0].dimension]

        for e in entities:
            assert isinstance(
                e,
                (
                    Point,
                    PointBase,
                    LineBase,
                    Surface,
                    PlaneSurface,
                    SurfaceBase,
                    Volume,
                    VolumeBase,
                ),
            ), "Can add physical groups only for Points, Lines, Surfaces, Volumes, not {}.".format(
                type(e)
            )
            assert d[e.dimension] == tpe

        label = self._new_physical_group(label)
        self._GMSH_CODE.append(
            "Physical {}({}) = {{{}}};".format(
                tpe, label, ", ".join([e.id for e in entities])
            )
        )
        return

else:
            top = Dummy(top)
            extruded = Dummy(extruded)

        lat = []
        # lateral surfaces can be deduced only if we start from a SurfaceBase
        # or a Polygon
        if isinstance(input_entity, (SurfaceBase, self.Polygon)):
            # out[0]` is the surface, out[1] the top, and everything after that
            # the sides, cf.
            # . Each
            # lateral surface has 4 edges: the one from input_entity, the one
            # from top, and the two lines (or splines) connecting their extreme
            # points.
            lat = [
                SurfaceBase("{}[{}]".format(name, i + 2), 4)
                for i in range(input_entity.num_edges)
            ]

        return top, extruded, lat

def __init__(self, id0=None, num_edges=0):
        if id0:
            assert isinstance(id0, str)
            self.id = id0
        else:
            self.id = f"s{SurfaceBase._ID}"
            SurfaceBase._ID += 1
        self.num_edges = num_edges
        return