hincrby and hget returning True instead of actual value in Redis (python)

For performance improvements, I have used the Redis pipeline instead of single insertions. Please find the code snippet for the same.

r = redis.Redis(connection_pool=redis_pool)
r_pipeline = r.pipeline()
for key in keys:
    r_pipeline.hincrby(key, hash, amount)
    r_pipeline.expire(key, Globals.Cache.ttl)
return r_pipeline.execute()

the return value of r_pipeline.execute() is a list. Based on the documentation it supposes to increment and return the incremented value. But sometimes it is actually returning the value and sometimes it is just returning True.

I have gone through the documentation and did google but still not able to figure out why hincrby is returning True in the pipeline.

Can someone please help.