Convert df.index.names to List[str] for list

Author: leehart

malariagen_data/anoph/frq_base.py

@@ -210,7 +210,9 @@ def plot_frequencies_heatmap(
 
         # Indexing.
         if index is None:
-            index = list(df.index.names)
+            # `list[Hashable]` is incompatible with `list`
+            index_names_as_list = [str(name) for name in df.index.names]
+            index = list(index_names_as_list)
         df = df.reset_index().copy()
         if isinstance(index, list):
             index_col = (