input: Write a function to print a pattern of asterisks that first increases in number up to 5 lines and then decreases back to 1 line.
  assert print_pattern()==None
  assert print_pattern()==None
  assert print_pattern()==None
  assert print_pattern()==None
  assert print_pattern()==None
output: def print_pattern():
      for i in range(1, 6):
          print('*' * i)
      for i in range(4, 0, -1):
          print('*' * i)