added __getitem__() and filter_nodes()to HamiltonGraph

[zilto]

Context

The graph_types.HamiltonGraph and graph_types.HamiltonNode are the public facing interfaces for the graph.FunctionGraph and node.Node. HamiltonNode should be accessed through a HamiltonGraph and not be constructed directly.

Motivation

The most common operations on the HamiltonGraph is selecting a single node or filtering them by a criteria. However, they're are no API for that, meaning some list comprehension or filter() are often implemented in the library code but also in the user's code. This motivated the implementation __getitem()__ and filter_nodes()

Changes

HamiltonGraph.__getitem()__ allows to get a node using it's name as key (we know the node name is unique). It does a simple dictionary lookup.

HamiltonGraph(...)["my_node"] == HamiltonNode(name="my_node", ...)

HamiltonGraph.filter_nodes() receives a filter argument which is a Callable that takes in a HamiltonNode and returns a boolean. That provides a lot of flexibility to be able to filter by name, type, tags, or any other attributes.

Other changes

Took the opportunity to implement a one line change for #865

How I tested this

• added tests for new functionalities
• all old tests are passing

Notes

Checklist

• PR has an informative and human-readable title (this will be pulled into the release notes)
• Changes are limited to a single goal (no scope creep)
• Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future TODOs are captured in comments
• Project documentation has been updated if adding/changing functionality.