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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 _organize_tools_on(data, is_cwl):
 """Ensure tools_on inputs match items specified elsewhere. """

    # want tools_on: [gvcf] if joint calling specified in CWL
    if is_cwl:
        if tz.get_in(["algorithm", "jointcaller"], data):
            val = tz.get_in(["algorithm", "tools_on"], data)
            if not val:
                val = []
            if not isinstance(val, (list, tuple)):
                val = [val]
            if "gvcf" not in val:
                val.append("gvcf")
            data["algorithm"]["tools_on"] = val
    return data