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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def combine_sample_regions(*samples):
 """Create batch-level sets of callable regions for multi-sample calling. Intersects all non-callable (nblock) regions from all samples in a batch, producing a global set of callable regions. """

    samples = utils.unpack_worlds(samples)
    samples = cwlutils.unpack_tarballs(samples, samples[0])
    # back compatibility -- global file for entire sample set
    global_analysis_file = os.path.join(samples[0]["dirs"]["work"], "analysis_blocks.bed")
    if utils.file_exists(global_analysis_file) and not _needs_region_update(global_analysis_file, samples):
        global_no_analysis_file = os.path.join(os.path.dirname(global_analysis_file), "noanalysis_blocks.bed")
    else:
        global_analysis_file = None
    out = []
    analysis_files = []
    batches = []
    with shared.bedtools_tmpdir(samples[0]):
        for batch, items in vmulti.group_by_batch(samples, require_bam=False).items():
            batches.append(items)
            if global_analysis_file:
                analysis_file, no_analysis_file = global_analysis_file, global_no_analysis_file
            else:
                analysis_file, no_analysis_file = _combine_sample_regions_batch(batch, items)
            for data in items:
                vr_file = dd.get_variant_regions(data)
                if analysis_file:
                    analysis_files.append(analysis_file)
                    data["config"]["algorithm"]["callable_regions"] = analysis_file
                    data["config"]["algorithm"]["non_callable_regions"] = no_analysis_file
                    data["config"]["algorithm"]["callable_count"] = pybedtools.BedTool(analysis_file).count()
                elif vr_file:
                    data["config"]["algorithm"]["callable_count"] = pybedtools.BedTool(vr_file).count()
                # attach a representative sample for calculating callable region
                if not data.get("work_bam"):
                    for x in items:
                        if x.get("work_bam"):
                            data["work_bam_callable"] = x["work_bam"]
                out.append([data])
        # Ensure output order matches input order, consistency for CWL-based runs
        assert len(out) == len(samples)
        sample_indexes = {dd.get_sample_name(d): i for i, d in enumerate(samples)}
        def by_input_index(xs):
            return sample_indexes[dd.get_sample_name(xs[0])]
        out.sort(key=by_input_index)
        if len(analysis_files) > 0:
            final_regions = pybedtools.BedTool(analysis_files[0])
            _analysis_block_stats(final_regions, batches[0])
    return out