ENH, TST: Cleans up `plotting.py` and adds new tests for `graph_utils.py`

[nawtrey]

Description

• General cleanup to plotting.py:

  • Replaces all == comparisons
  • Adds arc to arrows such that double arrows are differentiable
  • Standardizes edge drawing settings so all figures should be the same
  • Moves repeated code into smaller functions
  • Fixes issue with plotting.draw_cycles() where subplot scales were heterogeneous
  • Closes matplotlib figures so unclosed figures don't accumulate

• Changes to test_plotting.py:

  • Moves tests from test_plot_diagram to test_plot_diagrams since these are testing the same function
  • Adds additional test cases to test_plot_cycle and test_plot_diagrams to cover a few lines that were not previously being covered

• Adds test_add_attributes, test_generate_edges_errors, and test_ccw to test_kda.py

• Cleans up graph_utils.is_ccw() and graph_utils.get_ccw_cycle()

Status

• [x] Ready to go

[codecov[bot]]

Codecov Report

Merging #33 (fe4da3e) into master (6941f9b) will increase coverage by 2.21%. The diff coverage is 100.00%.

[nawtrey]

Overall this PR targeted the plotting.py module to clean it up, but there is still a lot to do there. At the moment the remaining 7 lines of code that aren't covered (out of 8 total) are for plt.savefig() calls, which we only really need 3 of in the module. This module should really have functions that handle all of the different cases (plot single, plot multiple, plot panel, etc.) which return the figure objects, and draw_diagrams/draw_cycles just handle the function calls and parameter inputs. That's a large task that isn't high priority at the moment, so I'll probably open an issue and deal with it later.

[nawtrey]

Okay, all the tests are passing and I've fixed all of the issues within the scope of this PR.

[nawtrey]

Merging.