Python - Wrike API. Creating new tasks (HELP)

 Hi,

I am trying to use python to create new tasks in Wrike. I am able to do this successfully but only for very basic fields such as title, description, and status. I am having trouble setting sub dicts, for example {"dates":{"start":"YYYY-MM-DD"}. Here's a sample of my code. When I try to add information for start and due dates I get status code 400.

def main():
    folderId = "folderIDnumber"
    headers = {'authorization': "bearer my_token_key"}
    url = "https://www.wrike.com/api/v3"
    data = formWrikeTaskJson(title="new task",
                             description="some details",
                             status=postStatus)
    rPost = post2wrike(folderId,headers,url,data)
    print rPost.status_code

def formWrikeTaskJson(title="New Task",description="",status="Active",customStatusId='',
                      starttime=datetime.datetime.today().strftime('%Y-%m-%d'),
                      endtime = datetime.datetime.today().strftime('%Y-%m-%d')):
    data = {}
    data["title"]=title
    data["description"]=description
    data["status"]=status

    #data["dates"]={"start":starttime} this part does not work!
    #data = json.dumps(data) neither does doing this in general
    return data

def post2wrike(folderId,headers,url,json):
    url = url+"/folders/{}/tasks".format(folderId)
    rPost = requests.post(url, headers=headers,data=json)
    return rPost