func_code: def search(str, letter):
      if str[i] == '':
          return False
      elif str[0] == letter:
          return True
      else:
          search(str[1:], letter)
annotation: def search(str, letter):
      if str == '':
          return False
      elif str[0] == letter:
          return True
      else:
          return search(str[1:], letter)
  