input: Write a function to print all combinations of elements from three given lists in a new line. The function should accept three lists as input and use nested loops to iterate through each combination of elements.
  assert nested_loop_combinations([1,2,3], [4,5,6], [7,8,9]) 
  # Expected 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_combinations(list1, list2, list3):
      for i in list1:
          for j in list2:
              for k in list3:
                  print(i, j, k)