input: Write a function to construct a nested loop in Python to print out the elements from three given lists, each element in the triplet (x, y, z) being printed on a new line. The given lists are [1,2,3], [4,5,6], and [7,8,9]. 
  
  assert nested_loop_print([1,2,3], [4,5,6], [7,8,9])==None
  assert nested_loop_print([0,1], [2,3], [4,5])==None
  assert nested_loop_print([1], [2], [3])==None
  assert nested_loop_print([], [], [])==None
output: def nested_loop_print(list1, list2, list3):
      for x in list1:
          for y in list2:
              for z in list3:
                  print(x, y, z)