input: Write a function to print a staircase of height 'n', where n is an integer. If the input is 5, the output should be a staircase with 5 steps.
  
  assert staircase(5)
  assert staircase(3)
  assert staircase(0)
  assert staircase(7)
  assert staircase(1)
output: def staircase(n):
      for i in range(1, n + 1):
          print(' ' * (n - i) + '#' * i)