conflicting types for错误

#coding=utf-8
import functools
import argparse
import os.path


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("-w", dest = "wfileName")
    parser.add_argument("-l", dest = "lfileName")    
    args = parser.parse_args()
    fileName = args.lfileName if args.wfileName is None else args.wfileName
    if not os.path.exists(fileName):
        print("file not found")

    with open(fileName, "rb") as f:
        data = bytearray(os.path.getsize(fileName))
        f.readinto(data)
        #print(data)
        if args.wfileName is not None:
            if data.find(b'\r\n') > 0:
                print('find windows signal')
            data = data.replace(b"\r\n", b"\n")
        else:
            if data.find(b'\n') > 0:
                print('find linux signal')
            data = data.replace(b"\n", b"\r\n")

    with open(fileName, "wb") as f:
        #print(data)
        f.write(data)


if __name__ == "__main__":
    main()