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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 file_list(load):
    '''
    Return a list of all files in a specified environment
    '''
    ret = set()
    try:
        for container in __opts__['azurefs']:
            if container.get('saltenv', 'base') != load['saltenv']:
                continue
            container_list = _get_container_path(container) + '.list'
            lk = container_list + '.lk'
            salt.fileserver.wait_lock(lk, container_list, 5)
            if not os.path.exists(container_list):
                continue
            with salt.utils.files.fopen(container_list, 'r') as fp_:
                ret.update(set(salt.utils.json.load(fp_)))
    except Exception as exc:
        log.error('azurefs: an error ocurred retrieving file lists. '
                  'It should be resolved next time the fileserver '
                  'updates. Please do not manually modify the azurefs '
                  'cache directory.')
    return list(ret)