Refactor cube_pool.py out of generate_draft_pool.py

WIll reuse for other modes of play

cube_pool.py

@@ -0,0 +1,29 @@
+# Loads disjoint pools from a cube CSV
+
+import csv
+from collections import defaultdict
+from typing import Dict, List, Set
+
+import cubecobra_csv
+
+
+def load_pools(csv_path: str, pool_tags: Set[str]) -> Dict[str, List[str]]:
+    pools = defaultdict(list)
+    with open(csv_path) as f:
+        reader = csv.reader(f)
+        header_line = next(reader)
+        cubecobra_csv.assert_header(header_line)
+        for line in reader:
+            card = line[cubecobra_csv.COLUMNS['Name']]
+            tags = set(line[cubecobra_csv.COLUMNS['Tags']].split(', '))
+            # print(f'{card} {tags}')
+            pool_tags_for_card = pool_tags.intersection(tags)
+            if len(pool_tags_for_card) == 0:
+                print(f'{card} does not have any of the tags: {pool_tags}')
+            elif len(pool_tags_for_card) == 1:
+                (pool_tag,) = pool_tags_for_card
+                pools[pool_tag].append(card)
+            else:
+                print(f'{card} should only be tagged as one in {pool_tags} '
+                      'but is tagged as {pool_tags_for_card}')
+    return pools