input: Write a function to print a staircase of height 'n', where each step is denoted by '#' and the width of each step increases from top to bottom, with the top step having 1 '#' and the bottom step having 'n' '#' characters. If 'n' is 0, print a newline character.
  
  assert staircase(5)==None
  assert staircase(0)==None
output: def staircase(n):
      for i in range(1, n + 1):
          print(' ' * (n - i) + '#' * i)
      if n == 0:
          print()