input: Write a python function to print each element in a nested list using two for loops.
  assert print_nested_elements([[1, 2, 3], [4, 5, 6], [7, 8, 9]])==None  # Should print 1 2 3 4 5 6 7 8 9
  assert print_nested_elements([['a', 'b'], ['c', 'd', 'e'], ['f']])==None  # Should print a b c d e f
  assert print_nested_elements([[10, 20], [30, 40], [50]])==None  # Should print 10 20 30 40 50
output: def print_nested_elements(nested_list):
      for sublist in nested_list:
          for item in sublist:
              print(item)