[Python] Fail to write nested data to Parquet via BigQuery API

I keep gettting the error in the title. any ideas on how to fix this issue? 

for company, credentials in loginCredentials.items():
password = credentials["Password"]
username = credentials["Username"]
Academy = company
Phase = credentials["Phase"]
values = {"grant_type": "password","username": username, "password": password}
data = urlencode(values).encode()
session = requests.Session()
session.headers =

{ 'Content-Type': 'application/x-www-form-urlencoded' }

response_body = session.post(TOKEN_API_URL, data=data)
access_token = json.loads(response_body.text)["access_token"]
#print(Academy " " str(response_body.status_code)+" "+response_body.reason)
session.headers = {
'Authorization': 'Bearer {}'.format(access_token)
}
#print(username + access_token)
learner_responses = session.get(LEARNER_API_URL)
learner_exclusions = session.get(LEARNER_EXCLUSIONS_URL)
#print(Academy + " "+ str(learner_responses.status_code) " " learner_responses.reason)
if learner_responses.status_code == 200:
response = json.loads(learner_responses.text)
learners = pd.DataFrame(response)
learners['Establishment_Name'] = Academy
learners['Establishment_Phase'] = Phase
entries.append(learners)
else:
continue

 

appended_data = pd.concat(entries, ignore_index=True)

 

from google.cloud import bigquery
project = 'aet-data-lake'
client = bigquery.Client(credentials=credentials, project=project)
dataset_ref = client.dataset('RAW')
table_ref = dataset_ref.table('Learners_AET')
job_config = bigquery.LoadJobConfig()
job_config.autodetect = True

client.load_table_from_dataframe(appended_data, table_ref,job_config=job_config).result()