<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _bowtie2_args_from_config(config, curcl):
 """Configurable high level options for bowtie2. """

    qual_format = config["algorithm"].get("quality_format", "")
    if qual_format.lower() == "illumina":
        qual_flags = ["--phred64-quals"]
    else:
        qual_flags = []
    num_cores = config["algorithm"].get("num_cores", 1)
    core_flags = ["-p", str(num_cores)] if num_cores > 1 else []
    user_opts = config_utils.get_resources("bowtie2", config).get("options", [])
    for flag_opt in (o for o in user_opts if str(o).startswith("-")):
        if flag_opt in curcl:
            raise ValueError("Duplicate option %s in resources and bcbio commandline: %s %s" %
                             flag_opt, user_opts, curcl)
    return core_flags + qual_flags + user_opts