show geometries for both categorical and numerical fields in the same plot - px.choropleth

I am trying to create a US county map (including AK and HI in the bottom corner of the continental map) in plotly. I do not have numerical data for every county. In fact I only have data for 50 counties (approx). I want the map to contain the geometry for the for the counties with not data, so I can plot them in a different color. Otherwise the map is to empty. I tried with add.trace but I could not make it work.

``
import plotly.graph_objs as go
import plotly.express as px
import pandas as pd
from urllib.request import urlopen
import json

with urlopen('https://raw.githubusercontent.com/plotly/datasets/master/geojson-counties-fips.json') as response:
counties = json.load(response)

df = pd.read_csv("https://raw.githubusercontent.com/plotly/datasets/master/fips-unemp-16.csv",
dtype={"fips": str})

df_nodata=df.loc[df.unemp <= 10]

df_nodata['categorical'] = 'no data'

df_data = df.loc[df.unemp > 10]

fig = px.choropleth(df_data,
geojson=counties,
locations=df_data.fips,
color=df_data.unemp,
scope='usa')

fig.add_trace(go.Figure(go.Choroplethmapbox(geojson=counties, locations=df_nodata.fips, z=df_nodata.categorical))
)

fig.show()

``
I am trying to combine the attached

layers.

Start by reproducing the example with px.choropleth and the attempted go.Choroplethmapbox trace, then inspect how these entry points compose geographic layers. The result should display counties with data and counties without data in the same US map, with the no-data counties using a distinct color.