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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_sentinel_val(v):
 """Retrieve expected sentinel value for an output, expanding records. """

    out = workflow.get_base_id(v["id"])
    if workflow.is_cwl_record(v):
        out += ":%s" % ";".join([x["name"] for x in _get_record_fields(v)])
    return out