TruncatingBigNumber can not be converted to an String

Traceback (most recent call last):
File "PATHTOFILE", line 10, in <module>
shard_it = kinesis.get_shard_iterator("newstream", shard_id, 'AT_TIMESTAMP', timestamp)["ShardIterator"]
File "C:\Python39\lib\site-packages\boto\kinesis\layer1.py", line 425, in get_shard_iterator
return self.make_request(action='GetShardIterator',
File "C:\Python39\lib\site-packages\boto\kinesis\layer1.py", line 877, in make_request
raise exception_class(response.status, response.reason,
boto.exception.JSONResponseError: JSONResponseError: 400 Bad Request
{'__type': 'SerializationException', 'Message': 'class com.amazon.coral.value.json.numbers.TruncatingBigNumber can not be converted to an String'}

I am making a python app that will collect data from kinesis and write it to a file. I want to read data after a certain period of time. so I am using the "AT_TIMESTAMP" in get_shard_iterator() method.
This function will be implemented in lambda.