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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_bgzip_cmd(config, is_retry=False):
 """Retrieve command to use for bgzip, trying to use bgzip parallel threads. By default, parallel bgzip is enabled in bcbio. If it causes problems please report them. You can turn parallel bgzip off with `tools_off: [pbgzip]` """

    num_cores = tz.get_in(["algorithm", "num_cores"], config, 1)
    cmd = config_utils.get_program("bgzip", config)
    if (not is_retry and num_cores > 1 and
          "pbgzip" not in dd.get_tools_off({"config": config})):
        cmd += " --threads %s" % num_cores
    return cmd