Paperspace access module tornado.web has no attribute 'asychronous'

Hi,

After installing Auto-Sklearn and TPOT, I cannot access jupyter notebook from web browser anymore.
The first page showing the jupyter notebook would show up, but once I click on the notebook. It show 505 Internal server error.

Here is the error message in paperspace.

Uncaught exception GET /notebooks/courses/ml1/bulldozer_linreg.ipynb (::1)
HTTPServerRequest(protocol=‘http’, host=‘localhost:8888’, method=‘GET’, uri=’/notebooks/courses/ml1/bulldozer_linreg.ipynb’, version=‘HTTP/1.1’, remote_ip=’::1’)
Traceback (most recent call last):
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/tornado/web.py”, line 1697, in _execute
result = method(*self.path_args, **self.path_kwargs)
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/tornado/web.py”, line 3174, in wrapper
return method(self, args, **kwargs)
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/notebook/notebook/handlers.py”, line 59, in get
get_custom_frontend_exporters=get_custom_frontend_exporters
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/notebook/base/handlers.py”, line 467, in render_template
return template.render(**ns)
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/jinja2/asyncsupport.py”, line 76, in render
return original_render(self, args, **kwargs)
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/jinja2/environment.py”, line 1008, in render
return self.environment.handle_exception(exc_info, True)
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/jinja2/environment.py”, line 780, in handle_exception
reraise(exc_type, exc_value, tb)
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/jinja2/_compat.py”, line 37, in reraise
raise value.with_traceback(tb)
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/notebook/templates/notebook.html”, line 1, in top-level template code
{% extends “page.html” %}
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/notebook/templates/page.html”, line 154, in top-level template code
{% block header %}
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/notebook/templates/notebook.html”, line 120, in block “header”
{% for exporter in get_custom_frontend_exporters() %}
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/notebook/notebook/handlers.py”, line 19, in get_custom_frontend_exporters
from nbconvert.exporters.base import get_export_names, get_exporter
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/nbconvert/init.py”, line 7, in
from . import postprocessors
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/nbconvert/postprocessors/init.py”, line 5, in
from .serve import ServePostProcessor
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/nbconvert/postprocessors/serve.py”, line 19, in
class ProxyHandler(web.RequestHandler):
File “/home/paperspace/anaconda3/envs/fastai/lib/python3.6/site-packages/nbconvert/postprocessors/serve.py”, line 21, in ProxyHandler
@web.asynchronous
AttributeError: module ‘tornado.web’ has no attribute ‘asynchronous’
[E 14:36:57.431 NotebookApp] {
“Host”: “localhost:8888”,
“Connection”: “keep-alive”,
“Upgrade-Insecure-Requests”: “1”,
“User-Agent”: “Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.121 Safari/537.36”,
“Accept”: "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,
/
;q=0.8",
“Referer”: “http://localhost:8888/tree/courses/ml1”,
“Accept-Encoding”: “gzip, deflate, br”,
“Accept-Language”: “en-US,en;q=0.9,zh-TW;q=0.8,zh;q=0.7”,
“Cookie”: "_xsrf=2|a47daf94|f71bf0b3b3872386bb2960f4ee3b3c4d|1550631948; username-localhost-8889=“2|1:0|10:1551998536|23:username-localhost-8889|44:OWQ2ZjJiNjQ4MDQ1NDM5OGFlYzZiNDcyMjE4MjVkZmE=|0b4bdd82de7541ecd2453ecd0538c05cc6cb683c64c049c2d3e3eaaa0196fa89”; username-localhost-8888=“2|1:0|10:1553193408|23:username-localhost-8888|44:ZmRlM2Q3ZGRhZTRjNDRkOTljNmIwZWQ1MDFlZGU4ZjU=|2c2198ea03f3bf3522cda006025ecce7cb0e063f52ab4ca7aca96d951945bf83"”
}
[E 14:36:57.431 NotebookApp] 500 GET /notebooks/courses/ml1/bulldozer_linreg.ipynb (::1) 94.65ms referer=http://localhost:8888/tree/courses/ml1

Please give me suggestion,

Thank you,

Fern