code: def lex(args):
      
      if len(args) == 0 or args[0] == SHOW:
          return [(SHOW, None)]
      elif args[0] == LOG:
          return [(LOG, None)]
      elif args[0] == ECHO:
          return [(ECHO, None)]
      elif args[0] == SET and args[1] == RATE:
          return tokenizeSetRate(args[2:])
      elif args[0] == SET and args[1] == DAYS:
          return tokenizeSetDays(args[2:])
      elif args[0] == TAKE:
          return tokenizeTake(args[1:])
      elif args[0] == CANCEL:
          return tokenizeCancel(args[1:])
      elif isMonth(args[0]):
          return tokenizeTake(args)
      else:
          print('Unknown commands: {}'.format(' '.join(args)))
          return []
docs: Lex input and return a list of actions to perform.