Token authentication failed: 'utf-8' codec can't decode byte 0xe4 in position 0: invalid continuation byte

Question

I'm trying to send the json data from azure ml to eventhub using codes below

import json
d = result.to_dict(orient='records')
data = json.dumps(d,ensure_ascii=False)

import asyncio
from azure.eventhub.aio import EventHubProducerClient
from azure.eventhub import EventData
import time
conn_sting = "Endpoint=***"
async def run():
producer = EventHubProducerClient.from_connection_string(conn_str=conn_string)
async with producer:

event_data_batch = await producer.create_batch(partition_id='0')
event_data_batch.add(EventData(data))


await producer.send_batch(event_data_batch)

nest_asyncio.apply()
loop = asyncio.get_event_loop()
loop.run_until_complete(run())
print("sent to eventhub")

and getting follwing error..

Token authentication failed: 'utf-8' codec can't decode byte 0xe4 in
position 0: invalid continuation byte
Token authentication failed: 'utf-8' codec can't decode byte 0xe4 in
position 0: invalid continuation byte

anyone could help debug the error? thanks