@fkiraly suggestion: add rule to differentiate nested_univ and Panel

yarnabrina · yarnabrina · commit e6ebe3cf9cf7 · 2024-07-07T22:04:55.000+05:30
diff --git a/sktime/datatypes/_panel/_check.py b/sktime/datatypes/_panel/_check.py
@@ -190,6 +190,14 @@ def check_pdmultiindex_panel(obj, return_metadata=False, var_name="obj", panel=T
         msg = f"{var_name} must have a MultiIndex, found {type(obj.index)}"
         return _ret(False, msg, None, return_metadata)
 
+    # check to delineate from nested_univ mtype (Hierarchical)
+    # pd.DataFrame mtype allows object dtype,
+    # but if we allow object dtype with Panel entries,
+    # the mtype becomes ambiguous, i.e., non-delineable from nested_univ
+    if np.prod(obj.shape) > 0 and isinstance(obj.iloc[0, 0], (pd.Series, pd.DataFrame)):
+        msg = f"{var_name} cannot contain nested pd.Series or pd.DataFrame"
+        return _ret(False, msg, None, return_metadata)
+
     index = obj.index
 
     # check that columns are unique
