I get below error!!!

[amrute]

werkzeug.exceptions.BadRequestKeyError
werkzeug.exceptions.BadRequestKeyError: 400 Bad Request: The browser (or proxy) sent a request that this server could not understand.
KeyError: 'superhero'

File "C:\Users\Shreekant\AppData\Local\Programs\Python\Python38-32\Lib\site-packages\flask\app.py", line 2463, in call
return self.wsgi_app(environ, start_response)
File "C:\Users\Shreekant\AppData\Local\Programs\Python\Python38-32\Lib\site-packages\flask\app.py", line 2449, in wsgi_app
response = self.handle_exception(e)
File "C:\Users\Shreekant\AppData\Local\Programs\Python\Python38-32\Lib\site-packages\flask\app.py", line 1866, in handle_exception
reraise(exc_type, exc_value, tb)
File "C:\Users\Shreekant\AppData\Local\Programs\Python\Python38-32\Lib\site-packages\flask_compat.py", line 39, in reraise
raise value
File "C:\Users\Shreekant\AppData\Local\Programs\Python\Python38-32\Lib\site-packages\flask\app.py", line 2446, in wsgi_app
response = self.full_dispatch_request()
File "C:\Users\Shreekant\AppData\Local\Programs\Python\Python38-32\Lib\site-packages\flask\app.py", line 1951, in full_dispatch_request
rv = self.handle_user_exception(e)
File "C:\Users\Shreekant\AppData\Local\Programs\Python\Python38-32\Lib\site-packages\flask\app.py", line 1820, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "C:\Users\Shreekant\AppData\Local\Programs\Python\Python38-32\Lib\site-packages\flask_compat.py", line 39, in reraise
raise value
File "C:\Users\Shreekant\AppData\Local\Programs\Python\Python38-32\Lib\site-packages\flask\app.py", line 1949, in full_dispatch_request
rv = self.dispatch_request()
File "C:\Users\Shreekant\AppData\Local\Programs\Python\Python38-32\Lib\site-packages\flask\app.py", line 1935, in dispatch_request
return self.view_functionsrule.endpoint
File "C:\Shreekant\GIT\LearningPython\UploadFile\src\app.py", line 19, in upload
folder_name = request.form['superhero']
File "C:\Users\Shreekant\AppData\Local\Programs\Python\Python38-32\Lib\site-packages\werkzeug\datastructures.py", line 442, in getitem
raise exceptions.BadRequestKeyError(key)
werkzeug.exceptions.BadRequestKeyError: 400 Bad Request: The browser (or proxy) sent a request that this server could not understand.
KeyError: 'superhero'
The debugger caught an exception in your WSGI application. You can now look at the traceback which led to the error.
To switch between the interactive traceback and the plaintext one, you can click on the "Traceback" headline. From the text traceback you can also create a paste of it. For code execution mouse-over the frame you want to debug and click on the console icon on the right side.

You can execute arbitrary Python code in the stack frames and there are some extra helpers available for introspection:

dump() shows all variables in the frame
dump(obj) dumps all that's known about the object