input: Write a function to print out the nested lists' elements in a new line using nested loops. The function should take a list of lists as input.
  assert nested_loop_print([[1,2,3], [4,5,6], [7,8,9]])==None
  # Output:
  # 1 4 7
  # 1 4 8
  # 1 4 9
  # 1 5 7
  # 1 5 8
  # 1 5 9
  # 1 6 7
  # 1 6 8
  # 1 6 9
  # 2 4 7
  # 2 4 8
  # 2 4 9
  # 2 5 7
  # 2 5 8
  # 2 5 9
  # 2 6 7
  # 2 6 8
  # 2 6 9
  # 3 4 7
  # 3 4 8
  # 3 4 9
  # 3 5 7
  # 3 5 8
  # 3 5 9
  # 3 6 7
  # 3 6 8
  # 3 6 9
output: def nested_loop_print(lst):
      for i in lst[0]:
          for j in lst[1]:
              for k in lst[2]:
                  print(i, j, k)