Example pyproject.toml and a docker file to show the issue with poetry erasing it's own dependencies

Dockerfile

FROM python:3.9.1
WORKDIR /code

COPY poetry.lock pyproject.toml ./
RUN pip install --upgrade pip && \
    pip install poetry && \
    poetry config virtualenvs.create false && \
    poetry install --no-dev

COPY . ./

CMD ["python", "app/main.py"]

pyproject.toml

[tool.poetry]
name = "example"
version = "0.0.0"
description = "example package"
authors = ["author@example.com"]

[tool.poetry.dependencies]
python = "^3.9"

[tool.poetry.dev-dependencies]
appdirs = "^1.4.4"

[build-system]
requires = ["poetry>=0.12"]
build-backend = "poetry.masonry.api"