Tests pandas module

[M-Lampert]

Graph Functionality Enhancements:

• Updated the to_undirected method in src/pathpyG/core/graph.py to manually handle undirected edge creation, ensuring compatibility with numpy-based edge attributes. Removed reliance on ToUndirected transform.

Temporal Graph Improvements:

• Introduced __getitem__ method in src/pathpyG/core/temporal_graph.py for accessing graph attributes, node attributes, and edge attributes using keys, including support for temporal edges.
• Added a tedge_to_index -map initialised in the __init__ method of src/pathpyG/core/temporal_graph.py, enabling mapping of edges with timestamps to their indices in edge_index.

DataFrame Parsing Enhancements:

• Refactoring by introducing a _parse_timestamp function in src/pathpyG/io/pandas.py to handle timestamp parsing and rescaling in DataFrame columns, improving code readability
• Enhanced _parse_df_column to support additional data types like lists and tuples, ensuring robust parsing of DataFrame attributes into graph data objects.

Logging and Error Handling:

• Replaced print statements with logger.debug or raised exceptions in src/pathpyG/io/pandas.py to improve error handling and debugging.

Testing

• Added tests to all functions in the pathpyG.io.pandas module, increasing the total code coverage by 3% 🎉