input: Write a function to print a pattern of asterisks as described in the instruction. The pattern should increase the number of asterisks in each line from 1 to 5 and then decrease back to 1.
  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)