code: def merge_variant_files(orig_files, out_file, ref_file, config, region=None):
      
      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
docs: 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).