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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 clean_fsbackend(opts):
    '''
    Clean out the old fileserver backends
    '''
    # Clear remote fileserver backend caches so they get recreated
    for backend in ('git', 'hg', 'svn'):
        if backend in opts['fileserver_backend']:
            env_cache = os.path.join(
                opts['cachedir'],
                '{0}fs'.format(backend),
                'envs.p'
            )
            if os.path.isfile(env_cache):
                log.debug('Clearing %sfs env cache', backend)
                try:
                    os.remove(env_cache)
                except OSError as exc:
                    log.critical(
                        'Unable to clear env cache file %s: %s',
                        env_cache, exc
                    )

            file_lists_dir = os.path.join(
                opts['cachedir'],
                'file_lists',
                '{0}fs'.format(backend)
            )
            try:
                file_lists_caches = os.listdir(file_lists_dir)
            except OSError:
                continue
            for file_lists_cache in fnmatch.filter(file_lists_caches, '*.p'):
                cache_file = os.path.join(file_lists_dir, file_lists_cache)
                try:
                    os.remove(cache_file)
                except OSError as exc:
                    log.critical(
                        'Unable to file_lists cache file %s: %s',
                        cache_file, exc
                    )