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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 _handle_precalled(data):
 """Copy in external pre-called variants fed into analysis. Symlinks for non-CWL runs where we want to ensure VCF present in a local directory. """

    if data.get("vrn_file") and not cwlutils.is_cwl_run(data):
        vrn_file = data["vrn_file"]
        if isinstance(vrn_file, (list, tuple)):
            assert len(vrn_file) == 1
            vrn_file = vrn_file[0]
        precalled_dir = utils.safe_makedir(os.path.join(dd.get_work_dir(data), "precalled"))
        ext = utils.splitext_plus(vrn_file)[-1]
        orig_file = os.path.abspath(vrn_file)
        our_vrn_file = os.path.join(precalled_dir, "%s-precalled%s" % (dd.get_sample_name(data), ext))
        utils.copy_plus(orig_file, our_vrn_file)
        data["vrn_file"] = our_vrn_file
    return data