ServersideOutputTransformation with multiple pages

Hello,
I want to create a multipage app with the ServersideOutputTransformation so that I can access data generated on one page on another page. For this, I have oriented on this instruction. I also tried this approach from the forum.
The usage of background callbacks as here in the example as well as in the documentation are not possible for me, because the callbacks should only be executed when triggered and not multiple times in the background

My goal is, that I can simply return a variable as an Output from a callback-function and use it somewhere in my application on any page. Just as long as the ID is mentioned as an input to the callback-function

The current code structure is as follows:
app.py:

import dash
from dash import Dash
import dash_bootstrap_components as dbc
from dash_extensions.enrich import DashProxy, Output, Input, State, Serverside, html, dcc, ServersideOutputTransform, FileSystemBackend

# styling the sidebar
SIDEBAR_STYLE = {}

LINK_STYLE = {}

PARAMETERS, APP = core.authFun.initiate(user=None)

app = DashProxy(__name__, use_pages=True, transforms=[ServersideOutputTransform()])


#definition of the sidebar. Use HTML components
sidebar = html.Div([])

app.layout = dbc.Container([
    dcc.Location(id='url', refresh=False),
    sidebar,

    dash.page_container

])

@app.callback(
        [
            ServersideOutput('oID', 'data'),
        ],
        Input('url', 'search'),
        background=True,
)
def getAADToken(queryParameter): #Just run on trigger input
    
    acquire_tokens_result = {'initial': 'runApp'}
    oID = ''

    if queryParameter != '' and 'code' in queryParameter:
        ...
        ...
        ...
        oID = 'just mocked, the value gets generated by function and is a String'

    return  oID 


if __name__ == '__main__':
    app.run(host = 'localhost', port = '8050', debug=True)

The file I want to use the contend of ‘oID’ is as follows:
adp.py

import dash
from dash_extensions.enrich import DashProxy, Output, Input, State, Serverside, html, dcc, ServersideOutputTransform, FileSystemBackend
import dash_bootstrap_components as dbc

dash.register_page(
        __name__,
        name = 'ADP',
        path = '/adp')

CONTENT_STYLE = {}

app = dash.get_app()


workspacesSelect = html.Tr([
    html.H2('Select a workspace:', style={'width': 550}), 
    dcc.Dropdown(
        id='workspaceDropdown',
    ),
])
...
...  I have left out the whole layout of the page because it is not relevant
...

#### Functions with callback
@app.callback(
        Output('workspaceDropdown', 'options'),
        [
            Input('url', 'pathname'),
            Input('oID', 'data')
        ],
)
def getWorkspaces(path, oID):
    try:
        if path == '/adp':
            workspaces = get_workspaces(oID) #here I want to use oID which I get from app.py
            workspacesList = list(workspaces.keys())

            return workspacesList
    except IndexError as e:
        None

    return []

The structure of my repository is as follows

app.py
*pages*
|--- adp.py
|--- otherpage.py

When I execute the code, I get the following Exception
Traceback (most recent call last):

  File "C:\Users\....\repo-folder\app.py", line 66, in <module>
    app = DashProxy(__name__, use_pages=True, transforms=[ServersideOutputTransform()])
  File "C:\Users\...\lib\site-packages\dash_extensions\enrich.py", line 358, in __init__
    super().__init__(*args, prevent_initial_callbacks=prevent_initial_callbacks, **kwargs)
  File "C:\Users\...\lib\site-packages\dash\dash.py", line 511, in __init__
    self.init_app()
  File "C:\Users\...\lib\site-packages\dash\dash.py", line 589, in init_app
    self.enable_pages()
  File "C:\Users\...\lib\site-packages\dash\dash.py", line 2040, in enable_pages
    _import_layouts_from_pages(self.config.pages_folder)
  File "C:\Users\...\lib\site-packages\dash\_pages.py", line 435, in _import_layouts_from_pages
    spec.loader.exec_module(page_module)
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "C:\Users\...\repo-folder\pages\adp.py", line 135, in <module>
    @app.callback(
  File "C:\Users\....\lib\site-packages\dash_extensions\enrich.py", line 364, in callback
    return self.blueprint.callback(*args, **kwargs)
AttributeError: 'DashProxy' object has no attribute 'blueprint'