Insert the text layer from text page 0 on to pdf_base at page_num

def _weave_layers_graft(
    *, pdf_base, page_num, text, font, font_key, procset, rotation, strip_old_text, log
):
    """Insert the text layer from text page 0 on to pdf_base at page_num"""

    log.debug("Grafting")
    if Path(text).stat().st_size == 0:
        return

    # This is a pointer indicating a specific page in the base file
    pdf_text = pikepdf.open(text)
    pdf_text_contents = pdf_text.pages[0].Contents.read_bytes()

    if not tesseract.has_textonly_pdf():
        # If we don't have textonly_pdf, edit the stream to delete the
        # instruction to draw the image Tesseract generated, which we do not
        # use.
        stream = bytearray(pdf_text_contents)
        pattern = b'/Im1 Do'
        idx = stream.find(pattern)
        stream[idx : (idx + len(pattern))] = b' ' * len(pattern)
        pdf_text_contents = bytes(stream)

    base_page = pdf_base.pages.p(page_num)

    # The text page always will be oriented up by this stage but the original
    # content may have a rotation applied. Wrap the text stream with a rotation
    # so it will be oriented the same way as the rest of the page content.
    # (Previous versions OCRmyPDF rotated the content layer to match the text.)
    mediabox = [float(pdf_text.pages[0].MediaBox[v]) for v in range(4)]
    wt, ht = mediabox[2] - mediabox[0], mediabox[3] - mediabox[1]

    mediabox = [float(base_page.MediaBox[v]) for v in range(4)]
    wp, hp = mediabox[2] - mediabox[0], mediabox[3] - mediabox[1]

    translate = pikepdf.PdfMatrix().translated(-wt / 2, -ht / 2)
    untranslate = pikepdf.PdfMatrix().translated(wp / 2, hp / 2)
    # -rotation because the input is a clockwise angle and this formula
    # uses CCW
    rotation = -rotation % 360
    rotate = pikepdf.PdfMatrix().rotated(rotation)

    # Because of rounding of DPI, we might get a text layer that is not
    # identically sized to the target page. Scale to adjust. Normally this
    # is within 0.998.
    if rotation in (90, 270):
        wt, ht = ht, wt
    scale_x = wp / wt
    scale_y = hp / ht

    log.debug('%r', (scale_x, scale_y))
    scale = pikepdf.PdfMatrix().scaled(scale_x, scale_y)

    # Translate the text so it is centered at (0, 0), rotate it there, adjust
    # for a size different between initial and text PDF, then untranslate
    ctm = translate @ rotate @ scale @ untranslate

    pdf_text_contents = b'q %s cm\n' % ctm.encode() + pdf_text_contents + b'\nQ\n'

    new_text_layer = pikepdf.Stream(pdf_base, pdf_text_contents)

    if strip_old_text:
        strip_invisible_text(pdf_base, base_page, log)

    base_page.page_contents_add(new_text_layer, prepend=True)

    _update_page_resources(
        page=base_page, font=font, font_key=font_key, procset=procset
    )
    pdf_text.close()