. Write a recursive method called subsets to find every possible sub-list
of a given list. A sub-list of a list L contains 0 or more of L’s elements.
Your method should accept a list of strings as its parameter and print
every sub-list that could be created from elements of that list, one per
line. For example, if the list stores [Janet, Robert, Morgan, Char],
the output from your method would be:
[Janet, Robert, Morgan, Char]
[Janet, Robert, Morgan]
[Janet, Robert, Char]
[Janet, Morgan, Char]
[Robert, Morgan, Char]
The order in which you show the sub-lists does not matter, and the order
of the elements of each sub-list also does not matter. The key thing is
that your method should produce the correct overall set of sub-lists as its
output. Notice that the empty list is considered one of these sub-lists.
You may assume that the list passed to your method is not null and that
the list contains no duplicates. Do not use any loops.