import re
s = '''<Operation dedupMode="normal" name="update">'''
print(re.sub(r'(?<=dedupMode=")(?:normal|accept|manual|review)(?=")', r"manual", s))
aW1wb3J0IHJlCnMgPSAnJyc8T3BlcmF0aW9uIGRlZHVwTW9kZT0ibm9ybWFsIiBuYW1lPSJ1cGRhdGUiPicnJwpwcmludChyZS5zdWIocicoPzw9ZGVkdXBNb2RlPSIpKD86bm9ybWFsfGFjY2VwdHxtYW51YWx8cmV2aWV3KSg/PSIpJywgciJtYW51YWwiLCBzKSkK