def common_feats(feats_lists):
    """
    Return a list with the common features of a list of 
    feature lists, e.g.:
    
    common_feats([['F', 'PL'], ['F', 'SG'], ['M', 'PL'], ['M', 'SG']])
    
    []
    
    This function does not necessarily preserve the original order of the features.
    """
    set_list=[set(feats) for feats in feats_lists]
    for s in set_list[1:]:
        set_list[0].intersection_update(s)
    return list(set_list[0])