fix drop duplicates

mapreader/download/sheet_downloader.py

@@ -557,7 +557,7 @@ def _save_metadata(
         if os.path.exists(out_filepath):
             existing_metadata_df = pd.read_csv(out_filepath, sep=",", index_col=0)
             metadata_df = pd.concat([existing_metadata_df, new_metadata_df], ignore_index=True)
-            metadata_df.drop_duplicates(keep="first", inplace=True)
+            metadata_df = metadata_df.loc[metadata_df.astype(str).drop_duplicates().index] # https://stackoverflow.com/questions/43855462/pandas-drop-duplicates-method-not-working-on-dataframe-containing-lists
         else: 
             metadata_df = new_metadata_df