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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 combine_hla_fqs(hlas, out_file, data):
 """OptiType performs best on a combination of all extracted HLAs. """

    if not utils.file_exists(out_file):
        with file_transaction(data, out_file) as tx_out_file:
            with open(tx_out_file, "w") as out_handle:
                for hla_type, hla_fq in hlas:
                    if utils.file_exists(hla_fq):
                        with open(hla_fq) as in_handle:
                            shutil.copyfileobj(in_handle, out_handle)
    return out_file