Document an example that directly uses session state about django-plotly-dash

[wlwatkins]

I don't know if this helps, but it's the teared down of my script for downloading a file.
download_file() is called by reverse('download_file') in the layout html via the urls.py. Here is the views.py and dash_app.py

views.py

from django.shortcuts import render
from django.http import HttpResponse

def homePage(request, **kwargs):
    request.session.flush

    context = {}
    dash_context = request.session.get("django_plotly_dash", dict())
    request.session['django_plotly_dash'] = dash_context
    from . import dash_app

    return render(request, template_name='index.html')

def download_file(request, **kwargs):
     var_1 = request.session['django_plotly_dash']["input_1"]
     var_2 = request.session['django_plotly_dash']["state_1"]

     # CREATE FILE FROM var_1 and var_2 e.g. csv etc...

    return HttpResponse(file)

dash_app.py

@app.expanded_callback(
    output = Output('output_div','children'),
    inputs = [Input('input_1','value')],
    state = [State('state_1', 'value')]
    )
def function_A(input_1, state_1, *args, **kwargs):

    kwargs['session_state']['input_1'] = input_1
    kwargs['session_state']['state_1'] =state_1

[GibbsConsulting]

PR #114 contains an example of using session state