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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 run_vardict(align_bams, items, ref_file, assoc_files, region=None, out_file=None):
 """Run VarDict variant calling. """

    items = shared.add_highdepth_genome_exclusion(items)
    if vcfutils.is_paired_analysis(align_bams, items):
        call_file = _run_vardict_paired(align_bams, items, ref_file,
                                        assoc_files, region, out_file)
    else:
        vcfutils.check_paired_problems(items)
        call_file = _run_vardict_caller(align_bams, items, ref_file,
                                        assoc_files, region, out_file)
    return call_file