def get_topic(core, topic_id):
url = get_url(core) + PersonalizedStream.TOPIC_PATH.format(Topic.generate_urn(core, topic_id))
headers = get_lf_token_header(core)
response = requests.get(url, headers = headers)
data = evaluate_response(response)['data']
return Topic.serialize_from_json(data['topic']) if 'topic' in data else None
