def combinations_list(list1):
    
    if len(list1) == 0:
        return [[]]
    result = []
    for el in combinations_list(list1[1:]):
        result += [el, el+[list1[0]]]
    return result
def combinations_list(el2):
    if len(el2) == 0:
        return [[]]
       
    result = []
    for el in combinations_list(el2[1:]):
        result += [el, el + [el2[0]]]
    return result