more tests, some fixes

- add "order_by" keyword to choose_correct_isoform
- support single glycans as input to choose_correct_isoform
- support triple-branch reordering in choose_correct_isoform and find_isomorphs
- renamed "hex" to "draw_hex"
- added the “drawing” argument to `draw_hex`, `hex_circumference`, `add_bond`, `add_sugar`, and `draw_bracket`
- made sure in `network_alignment` that only nodes that are virtual in all aligned networks stay virtual
- `choose_leaves_to_extend` will now correctly return no leaf node glycan if the target composition cannot be reached from any of the leaf nodes in a network

.gitignore

@@ -127,6 +127,7 @@ Thumbs.db
 
 # pytest
 .pytest_cache
+*.pdb
 
 # tools/trust-doc-nbs
 docs_src/.last_checked

glycowork/ml/model_training.py

@@ -1,6 +1,5 @@
 import copy
 import time
-import math
 from typing import Any, Callable, Dict, List, Optional, Tuple, Union
 import numpy as np
 import pandas as pd