Update load_markers.py

Author: ktroule

sctools/tools/load_markers.py

@@ -42,6 +42,6 @@ def load_markers(cell = None, group = None, tech = None, tissue = None, group_co
                             markers_df['Tissue'].isin(tissue)].copy()
 
 
-    markers_dict = markers_df.groupby('Cell')[group_cols].apply(list).to_dict()
+    markers_dict = markers_df.groupby(group_cols)['Gene'].apply(list).to_dict()
 
     return markers_df, markers_dict