Highlight - Simple grep tool that highlights instead of displaying only results

higlight.py

#!/usr/bin/env python3

from colorama import init, Fore, Back, Style
import sys
import argparse

init(autoreset=True)
what_color = Fore.BLACK + Back.WHITE

parser = argparse.ArgumentParser(exit_on_error=False)
parser.add_argument('search_string')
args = parser.parse_args()

for line in sys.stdin:
    if args.search_string in str(line):
        search_string    = args.search_string
        highlight_string = what_color + search_string + Style.RESET_ALL
        splitted = line.split(search_string)
        unsplit = highlight_string.join(splitted)
        print(unsplit)
    else:
        print(line)%