fix: 7 - define inflow_t before branch so it is always assigned

[daniel-rdt]

Changes proposed in this Pull Request

This PR addresses a pylint inconsistency in add_electricity in attach_hydro where inflow_t is only defined in a branch but used outside of it. This PR makes this explicit by defining inflow_t as an empty Dataframe before the branch. This also means an existing pylint: disable=E0606 could be removed.

Tasks

• Possibly upstream this change as the related code is not open-tyndp specific

Workflow

Open issues

• Failing CI due to https error

Notes

Checklist

• Security scan(s) show no high-severity bugs, critical vulnerabilities, or exposed secrets.
• I tested my contribution locally and it works as intended.
• Code and workflow changes are sufficiently documented.
• Changed dependencies are added to pixi.toml (using pixi add <dependency-name>).
• Changes in configuration options are added in config/config.default.yaml.
• Changes in configuration options are documented in doc/configtables/*.csv.
• Changes in configuration options are added in config/test/*.yaml.
• The multiple weather/climate years test is passing locally (using pixi run -e open-tyndp tyndp-cyears-test).
• Open-TYNDP SPDX license header added to all touched files.
• For new data sources or versions, these instructions have been followed.
• New rules are documented in the appropriate doc/*.rst files.
• A release note doc/release_notes.rst is added.
• Major features are documented with up-to-date information in doc/index.rst.
• Module docstrings added to new Python scripts.

[tgilon]

Thanks, probably good to upstream

[daniel-rdt]

Upstream PR opened in PyPSA#2224