def merge_variant_files(orig_files, out_file, ref_file, config, region=None):
    """Combine multiple VCF files with different samples into a single output file.

    Uses bcftools merge on bgzipped input files, handling both tricky merge and
    concatenation of files. Does not correctly handle files with the same
    sample (use combine_variant_files instead).
    """
    in_pipeline = False
    if isinstance(orig_files, dict):
        file_key = config["file_key"]
        in_pipeline = True
        orig_files = orig_files[file_key]
    out_file = _do_merge(orig_files, out_file, config, region)
    if in_pipeline:
        return [{file_key: out_file, "region": region, "sam_ref": ref_file, "config": config}]
    else:
        return out_file
Combine multiple VCF files with different samples into a single output file.

    Uses bcftools merge on bgzipped input files, handling both tricky merge and
    concatenation of files. Does not correctly handle files with the same
    sample (use combine_variant_files instead).