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