Process in three phases?

scripts/add_bwb_covers.py

@@ -25,7 +25,7 @@
 1. Phase 1 needs read access to BWB zipfiles in ol-home0:/1/var/tmp/imports/2022/covers
 2. slow_edition_needs_a_cover() takes a long time to find each Open Library Edition.
 3. fast_edition_needs_a_cover() required direct access to web.ctx.site.things().
-4. Could read many methods of access accellerate the edition_needs_a_cover() process?
+4. Could read-many methods of access accelerate the edition_needs_a_cover() process?
 """
 from __future__ import annotations
 
@@ -74,18 +74,18 @@ def generate_covers_dict(covers_dir: Path = COVERS_DIR) -> dict:
     the zip files in covers_dir.  This process currently takes about 17 sec to generate
     a dict containing 1.3M ISBN-13s.
 
-    {'Apr2022_1_lc_13.zip': [{'9780000528742': ''},
-                             {'9780006499268': ''},
-                             {'9780006499305': ''},
+    {'Apr2022_1_lc_13.zip': [{'9780000528742': []},
+                             {'9780006499268': []},
+                             {'9780006499305': []},
     """
     from operator import attrgetter
 
-    def get_isbn_13s_from_zipfile(zipfile_path: Path) -> Iterator[dict[str, str]]:
+    def get_isbn_13s_from_zipfile(zipfile_path: Path) -> Iterator[dict[str, list]]:
         with ZipFile(zipfile_path) as in_file:
             for cover_file in sorted(in_file.infolist(), key=attrgetter("filename")):
                 parts = cover_file.filename.split(".")  # 9780425030134.jpg
                 assert parts[-1] == "jpg", cover_file.filename
-                yield {parts[0]: ""}
+                yield {parts[0]: []}
 
     return {
         zipfile_path.name: list(get_isbn_13s_from_zipfile(zipfile_path))