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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 features():
    '''
    List currently available BTRFS features.

    CLI Example:

    .. code-block:: bash

        salt '*' btrfs.mkfs_features
    '''
    out = __salt__['cmd.run_all']("mkfs.btrfs -O list-all")
    salt.utils.fsutils._verify_run(out)

    ret = {}
    for line in [re.sub(r"\s+", " ", line) for line in out['stderr'].split("\n") if " - " in line]:
        option, description = line.split(" - ", 1)
        ret[option] = description

    return ret