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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_persistent_modules():
    '''
    Returns a list of modules in loader.conf that load on boot.
    '''
    mods = set()
    with salt.utils.files.fopen(_LOADER_CONF, 'r') as loader_conf:
        for line in loader_conf:
            line = salt.utils.stringutils.to_unicode(line)
            line = line.strip()
            mod_name = _get_module_name(line)
            if mod_name:
                mods.add(mod_name)
    return mods