NoLayoutException on deployment of multi page dash app example code

Hi,

I have copied the multipage example from Dash and my Dockerfile:

FROM python:3.7

# Create a working directory.
RUN mkdir wd
WORKDIR wd

# Install Python dependencies.
COPY requirements.txt .
RUN pip3 install -r requirements.txt

# Copy the rest of the codebase into the image
COPY . ./

# Finally, run gunicorn.
CMD [ "gunicorn", "--workers=5", "--threads=1", "-b 0.0.0.0:8000", "index:app.server"]

But i get the error:

 Failed to parse 'app.server' as an attribute name or function call.

Have anybody solved this?