input: Write a function to generate a staircase of height 'n' where 'n' is an integer. The function should print a staircase with 'n' steps using the character '#'. Each step should be left-aligned with spaces preceding the '#' characters.
  assert staircase(5) == None
  assert staircase(3) == None
  assert staircase(1) == None
  assert staircase(0) == None
  assert staircase(7) == None
output: def staircase(n):
      for i in range(1, n + 1):
          print(' ' * (n - i) + '#' * i)