sample() will output a list of lists

Suppose I set the list l = range(100). I know that random.sample(l, 20) will spit a random list similar to [80, 90, 66, 37, 7, 34, 9, 33, 69, 35, 87, 39, 47, 68, 41, 51, 10, 52, 42, 11]. I would need to sample from the same list, but in the different way. This time, the sample() function has to output a list where each element is a list of consecutive numbers. For instance, the output of sample(range(100), 3, 4) might be [[4, 5, 6, 7], [12, 13, 14, 15], [60, 61, 62, 63]]. How can I do that

UPDATE

If the list is list_inst=[12, 8, 0, 12, 19, 20, 13, 19, 78, 21, 13, 85], than sample(list_inst, 3, 4) might output [[12, 8, 0, 12], [0, 12, 19, 20], [13, 19, 78, 21]].