Get known BTRFS formatted devices on the system.

    CLI Example:

    .. code-block:: bash

        salt '*' btrfs.devices

def devices():
    '''
    Get known BTRFS formatted devices on the system.

    CLI Example:

    .. code-block:: bash

        salt '*' btrfs.devices
    '''
    out = __salt__['cmd.run_all']("blkid -o export")
    salt.utils.fsutils._verify_run(out)

    return salt.utils.fsutils._blkid_output(out['stdout'], fs_type='btrfs')