In the test, the index is duplicated, causing .at to return multiple …

…rows, which is incorrect

Use .loc instead which is designed to return multiple rows
now returns series instead of np array

allensdk/test_utilities/custom_comparators.py

@@ -110,11 +110,11 @@ def safe_df_comparison(expected: pd.DataFrame,
             msg += '\nindex mismatch in non-null when checking '
             msg += f'{col}\n'
         for index_val in expected_valid.index.values:
-            e = expected_valid.at[index_val, col]
-            o = obtained_valid.at[index_val, col]
-            if isinstance(e, np.ndarray):
+            e = expected_valid.loc[index_val, col]
+            o = obtained_valid.loc[index_val, col]
+            if isinstance(e, pd.Series):
                 e = list(e)
-            if isinstance(o, np.ndarray):
+            if isinstance(o, pd.Series):
                 o = list(o)
             if not e == o:
                 msg += f'\n{col}\n'