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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 export_theta(ckout, data):
 """Provide updated set of data with export information for TheTA2 input. """

    cns_file = chromhacks.bed_to_standardonly(ckout["cns"], data, headers="chromosome")
    cnr_file = chromhacks.bed_to_standardonly(ckout["cnr"], data, headers="chromosome")
    out_file = "%s-theta.input" % utils.splitext_plus(cns_file)[0]
    if not utils.file_exists(out_file):
        with file_transaction(data, out_file) as tx_out_file:
            cmd = [_get_cmd(), "export", "theta", cns_file, cnr_file, "-o", tx_out_file]
            do.run(_prep_cmd(cmd, tx_out_file), "Export CNVkit calls as inputs for TheTA2")
    ckout["theta_input"] = out_file
    return ckout