How to use the xcffib.xproto.GC function in xcffib

def create_gc(conn):
    """Creates a simple graphics context"""
    gc = conn.generate_id()
    default_screen = conn.setup.roots[conn.pref_screen]

    conn.core.CreateGC(
        gc, default_screen.root,        # gc id, drawable
        GC.Foreground | GC.Background,  # value mask
        [                               # value list
            default_screen.black_pixel,
            default_screen.white_pixel
        ]
    )

    return gc

self.xsetup.roots[0].root,
                                          0, 0, self.width, self.height,
                                          0, WindowClass.InputOutput,
                                          self.xsetup.roots[0].root_visual,
                                          CW.BackPixel | CW.EventMask,
                                          events)

        self.connection.core.CreatePixmap(self.xsetup.roots[0].root_depth,
                                          self.pixmap,
                                          self.xsetup.roots[0].root,
                                          self.width,
                                          self.height)

        self.connection.core.CreateGC(self.gc,
                                      self.xsetup.roots[0].root,
                                      GC.Foreground | GC.Background,
                                      [self.xsetup.roots[0].black_pixel,
                                       self.xsetup.roots[0].white_pixel])

        self.surface = cairo.XCBSurface (self.connection,
                                         self.pixmap,
                                         self.xsetup.roots[0].allowed_depths[0].visuals[0],
                                         self.width,
                                         self.height)
        self.context = cairo.Context(self.surface)
        self.surfaces = {"screen":self.surface}
        self.contexts = {"screen":self.context}
        self.layers = OrderedDict() #Layer roots
        self.lastupdate = {}
        self.lastdrawn = {}

self.wid, self.width, self.height = wid, width, height

        self.pixmap = self.qtile.conn.conn.generate_id()
        self.gc = self.qtile.conn.conn.generate_id()

        self.qtile.conn.conn.core.CreatePixmap(
            self.qtile.conn.default_screen.root_depth,
            self.pixmap,
            self.wid,
            self.width,
            self.height
        )
        self.qtile.conn.conn.core.CreateGC(
            self.gc,
            self.wid,
            xcffib.xproto.GC.Foreground | xcffib.xproto.GC.Background,
            [
                self.qtile.conn.default_screen.black_pixel,
                self.qtile.conn.default_screen.white_pixel
            ]
        )
        self.surface = cairocffi.XCBSurface(
            qtile.conn.conn,
            self.pixmap,
            self.find_root_visual(),
            self.width,
            self.height,
        )
        self.ctx = self.new_ctx()
        self.clear((0, 0, 1))