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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 _get_interval(variant_regions, region, out_file, items):
 """Retrieve interval to run analysis in. Handles no targets, BED and regions region can be a single region or list of multiple regions for multicore calling. """

    target = shared.subset_variant_regions(variant_regions, region, out_file, items)
    if target:
        if isinstance(target, six.string_types) and os.path.isfile(target):
            return "--interval %s" % target
        else:
            return "--interval %s" % bamprep.region_to_gatk(target)
    else:
        return ""