Issue on page /notebooks/04/power-network.html

[nfbvs]

• Issues with objective sense: In the 'Optimal Power Flow' section the problem is stated as a maximization problem. In the 'Solving OPF' section the problem is declared as a minimization problem but implemented as a maximization one.
• Potential typo in OPF2: def generation_upperound(m, i): should probably be def generation_upper_bound(m, i):
• Docstring of OPF functions: docstring mentions the return of two dictionaries but the functions are returning the objective

Probably also relevant: in nodes.csv the first (nameless) column is a duplicate of the node_id column. This column is used as an index, but has duplicated values.

[alessandrozocca]

Thank you for catching all these typos and inconsistencies. The latest commit fixes them.

The .csv file is indeed imported with a dubious choice for the index, but I believe it doesn't cause any issues in the notebook.