Merge pull request #16007 from mvdbeek/backport_bam_fix

            try:

                with pysam.AlignmentFile(dataset.file_name, "rb", check_sq=False) as bamfile:

                    ck_size = 300  # 300 lines

                    ck_data = ""

                    header_line_count = 0

                    if offset == 0:

                        ck_data = bamfile.text.replace("\t", " ")  # type: ignore[attr-defined]

                        header_line_count = bamfile.text.count("\n")  # type: ignore[attr-defined]

                        offset = bamfile.tell()

                        ck_lines = bamfile.text.strip().replace("\t", " ").splitlines()  # type: ignore[attr-defined]

                    else:

                        bamfile.seek(offset)

                    for line_number, alignment in enumerate(bamfile):

                        ck_lines = []

                    for line_number, alignment in enumerate(bamfile, len(ck_lines)):

                        # return only Header lines if 'header_line_count' exceeds 'ck_size'

                        # FIXME: Can be problematic if bam has million lines of header

                        offset = bamfile.tell()

                        if (line_number + header_line_count) > ck_size:

                        if line_number > ck_size:

                            break

                        else:

                        offset = bamfile.tell()

                        bamline = alignment.tostring(bamfile)

                            # Galaxy display each tag as separate column because 'tostring()' funcition put tabs in between each tag of tags column.

                            # Below code will remove spaces between each tag.

                            bamline_modified = ("\t").join(bamline.split()[:11] + [(" ").join(bamline.split()[11:])])

                            ck_data = f"{ck_data}\n{bamline_modified}"

                        # With multiple tags, Galaxy would display each as a separate column

                        # because the 'tostring()' function uses tabs also between tags.

                        # Below code will turn these extra tabs into spaces.

                        n_tabs = bamline.count("\t")

                        if n_tabs > 11:

                            bamline, *extra_tags = bamline.rsplit("\t", maxsplit=n_tabs - 11)

                            bamline = f"{bamline} {' '.join(extra_tags)}"

                        ck_lines.append(bamline)

                    else:

                        # Nothing to enumerate; we've either offset to the end

                        # of the bamfile, or there is no data. (possible with

                        # header-only bams)

                        offset = -1

                    ck_data = "\n".join(ck_lines)

            except Exception as e:

                offset = -1

                ck_data = f"Could not display BAM file, error was:\n{e}"