How to use the cairocffi.FONT_WEIGHT_BOLD function in cairocffi

def paint_text(text, w, h, rotate=False, ud=False, multi_fonts=False):
    surface = cairo.ImageSurface(cairo.FORMAT_RGB24, w, h)
    with cairo.Context(surface) as context:
        context.set_source_rgb(1, 1, 1)  # White
        context.paint()
        # this font list works in CentOS 7
        if multi_fonts:
            fonts = ['Century Schoolbook', 'Courier', 'STIX', 'URW Chancery L', 'FreeMono']
            context.select_font_face(np.random.choice(fonts), cairo.FONT_SLANT_NORMAL,
                                     np.random.choice([cairo.FONT_WEIGHT_BOLD, cairo.FONT_WEIGHT_NORMAL]))
        else:
            context.select_font_face('Courier', cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_BOLD)
        context.set_font_size(25)
        box = context.text_extents(text)
        border_w_h = (4, 4)
        if box[2] > (w - 2 * border_w_h[1]) or box[3] > (h - 2 * border_w_h[0]):
            raise IOError('Could not fit string into image. Max char count is too large for given image width.')

        # teach the RNN translational invariance by
        # fitting text box randomly on canvas, with some room to rotate
        max_shift_x = w - box[2] - border_w_h[0]
        max_shift_y = h - box[3] - border_w_h[1]
        top_left_x = np.random.randint(0, int(max_shift_x))
        if ud:
            top_left_y = np.random.randint(0, int(max_shift_y))
        else:
            top_left_y = h // 2
        context.move_to(top_left_x - int(box[0]), top_left_y - int(box[1]))

def paint_text(self, text, w, h, rotate=False, ud=False, multi_fonts=False):
        surface = cairo.ImageSurface(cairo.FORMAT_RGB24, w, h)
        with cairo.Context(surface) as context:
            context.set_source_rgb(1, 1, 1)  # White
            context.paint()
            # this font list works in CentOS 7
            if multi_fonts:
                fonts = ['Century Schoolbook', 'Courier', 'STIX', 'URW Chancery L', 'FreeMono']
                context.select_font_face(np.random.choice(fonts), cairo.FONT_SLANT_NORMAL,
                                         np.random.choice([cairo.FONT_WEIGHT_BOLD, cairo.FONT_WEIGHT_NORMAL]))
            else:
                context.select_font_face('Courier', cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_BOLD)
            context.set_font_size(25)
            box = context.text_extents(text)
            border_w_h = (4, 4)
            if box[2] > (w - 2 * border_w_h[1]) or box[3] > (h - 2 * border_w_h[0]):
                raise IOError('Could not fit string into image. Max char count is too large for given image width.')

            # teach the RNN translational invariance by
            # fitting text box randomly on canvas, with some room to rotate
            max_shift_x = w - box[2] - border_w_h[0]
            max_shift_y = h - box[3] - border_w_h[1]
            top_left_x = np.random.randint(0, int(max_shift_x))
            if ud:
                top_left_y = np.random.randint(0, int(max_shift_y))
            else:
                top_left_y = h // 2
            context.move_to(top_left_x - int(box[0]), top_left_y - int(box[1]))

with cairo.Context(surface) as context:
        context.set_source_rgb(1, 1, 1)  # White
        context.paint()
        # this font list works in CentOS 7
        if multi_fonts:
            fonts = [
                'Century Schoolbook', 'Courier', 'STIX',
                'URW Chancery L', 'FreeMono']
            context.select_font_face(
                np.random.choice(fonts),
                cairo.FONT_SLANT_NORMAL,
                np.random.choice([cairo.FONT_WEIGHT_BOLD, cairo.FONT_WEIGHT_NORMAL]))
        else:
            context.select_font_face('Courier',
                                     cairo.FONT_SLANT_NORMAL,
                                     cairo.FONT_WEIGHT_BOLD)
        context.set_font_size(25)
        box = context.text_extents(text)
        border_w_h = (4, 4)
        if box[2] > (w - 2 * border_w_h[1]) or box[3] > (h - 2 * border_w_h[0]):
            raise IOError(('Could not fit string into image.'
                           'Max char count is too large for given image width.'))

        # teach the RNN translational invariance by
        # fitting text box randomly on canvas, with some room to rotate
        max_shift_x = w - box[2] - border_w_h[0]
        max_shift_y = h - box[3] - border_w_h[1]
        top_left_x = np.random.randint(0, int(max_shift_x))
        if ud:
            top_left_y = np.random.randint(0, int(max_shift_y))
        else:
            top_left_y = h // 2

def paint_text(text, w, h, rotate=False, ud=False, multi_fonts=False):
    surface = cairo.ImageSurface(cairo.FORMAT_RGB24, w, h)
    with cairo.Context(surface) as context:
        context.set_source_rgb(1, 1, 1)  # White
        context.paint()
        # this font list works in Centos 7
        if multi_fonts:
            fonts = ['Century Schoolbook', 'Courier', 'STIX', 'URW Chancery L', 'FreeMono']
            context.select_font_face(np.random.choice(fonts), cairo.FONT_SLANT_NORMAL,
                                     np.random.choice([cairo.FONT_WEIGHT_BOLD, cairo.FONT_WEIGHT_NORMAL]))
        else:
            context.select_font_face('Courier', cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_BOLD)
        context.set_font_size(25)
        box = context.text_extents(text)
        border_w_h = (4, 4)
        if box[2] > (w - 2 * border_w_h[1]) or box[3] > (h - 2 * border_w_h[0]):
            raise IOError('Could not fit string into image. Max char count is too large for given image width.')

        # teach the RNN translational invariance by
        # fitting text box randomly on canvas, with some room to rotate
        max_shift_x = w - box[2] - border_w_h[0]
        max_shift_y = h - box[3] - border_w_h[1]
        top_left_x = np.random.randint(0, int(max_shift_x))
        if ud:
            top_left_y = np.random.randint(0, int(max_shift_y))
        else:
            top_left_y = h // 2
        context.move_to(top_left_x - int(box[0]), top_left_y - int(box[1]))

context.rectangle(xP, yP, cellSize, cellSize)
            context.stroke()
context.translate(pageWidth / 2, pageHeight / 2)
context.rotate(-angle)
context.translate(-pageWidth / 2, -pageHeight / 2)

if showLabel:
    log('Drawing label...')

    pageSize = min(pageWidth, pageHeight)  # enables a kind of responsive design

    # format fun facts and compute height of label based on number of lines
    funFactsLines = []
    labelHeight = 0.14*pageSize
    if funFacts:
        context.select_font_face(font, cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_BOLD)
        context.set_font_size(0.015*pageSize)
        context.set_source_rgb(0, 0, 0)
        funFacts =  ' '.join(funFacts).split(' ')

        # split long string into lines depending on page width
        i = 0
        while funFacts:
            rest = []
            lineWidth = context.text_extents(' '.join(funFacts))[2]
            while lineWidth > pageWidth - 0.2 * pageSize:
                rest.insert(0, funFacts[-1])
                funFacts = funFacts[:-1]
                lineWidth = context.text_extents(' '.join(funFacts))[2]
            funFactsLines.append(' '.join(funFacts))
            funFacts = rest
            i += 1

gradient.add_color_stop_rgba(0, 0, 0, 0, 0.21)
    gradient.add_color_stop_rgba(1, 0, 0, 0, 0.0)
    context.rectangle(0, 0.9*pageHeight, pageWidth, 0.006*pageSize)
    context.set_source(gradient)
    context.fill()

    # draw text
    context.move_to(0.1*pageSize, 0.9*pageHeight-labelHeight+0.0895*pageSize)
    context.select_font_face(font, cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_BOLD)
    context.set_font_size(0.054*pageSize)
    context.set_source_rgb(0, 0, 0)
    context.show_text(u'RULE {}'.format(rule))

    # draw fun facts
    if funFactsLines:
        context.select_font_face(font, cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_BOLD)
        context.set_font_size(0.015*pageSize)
        context.set_source_rgb(0, 0, 0)
        for i, l in enumerate(funFactsLines):
            context.move_to(0.1*pageSize, 0.9*pageHeight - labelHeight + 0.14*pageSize + i*funFactLineHeight*1.5)
            context.show_text(l)

    # draw rule icons (only for simple rules, would not be not legible for
    # "higher" rules)
    if currentStateWidth == 3:
        xOffset = pageWidth-0.115*pageSize
        yOffset = 0.9*pageHeight-labelHeight+0.056*pageSize
        cellSize = pageSize/78

        context.set_line_width(cellSize / 10)
        context.set_source_rgb(0, 0, 0)
        for neighbors in sorted(transistions.keys()):

def textwidth(self, text, config):
        """Calculates the width of the specified text.
        """
        surface = cairo.SVGSurface(None, 1280, 200)
        ctx = cairo.Context(surface)
        ctx.select_font_face(config['font_face'],
                             cairo.FONT_SLANT_NORMAL,
                             cairo.FONT_WEIGHT_BOLD)
        ctx.set_font_size(int(config['font_size']))
        return ctx.text_extents(text)[2] + 2

def drawText():
        fill = Image.colorRGB(50, 50, 50)

        title_font_size = cover_width * 0.08
        subtitle_font_size = cover_width * 0.05
        title_font_properties = (title_font_size, cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_BOLD)
        subtitle_font_properties = (subtitle_font_size, cairo.FONT_SLANT_NORMAL,
                                     cairo.FONT_WEIGHT_NORMAL)
        title_font_family = select_font(title)
        subtitle_font_family = select_font(subtitle)
        title_font_properties = scale_font(title, title_font_family, title_font_properties)
        subtitle_font_properties = scale_font(
            subtitle,
            subtitle_font_family,
            subtitle_font_properties
        )
        title_font = cover_image.font(title_font_family, title_font_properties)
        subtitle_font = cover_image.font(subtitle_font_family, subtitle_font_properties)
        title_height = (cover_height - cover_width - (cover_height * cover_margin / 100)) * 0.75

        x = cover_height * cover_margin / 100
        y = cover_height * cover_margin / 100 * 2