fix: Avoid using iter_rows in _check_dataframe_all_leaves to enable cuDF input

Author: MarcoGorelli

Diff for: packages/python/plotly/plotly/express/_core.py

@@ -1858,17 +1858,20 @@ def _check_dataframe_all_leaves(df: nw.DataFrame) -> None:
         null_mask=nw.any_horizontal(nw.all())
     ).get_column("null_mask")
 
-    for row_idx, row in zip(
-        null_indices_mask, null_mask.filter(null_indices_mask).iter_rows()
-    ):
-
-        i = row.index(True)
-
-        if not all(row[i:]):
-            raise ValueError(
-                "None entries cannot have not-None children",
-                df_sorted.row(row_idx),
+    null_mask_filtered = null_mask.filter(null_indices_mask)
+    if not null_mask_filtered.is_empty():
+        for col_idx in range(1, null_mask_filtered.shape[1]):
+            # For each row, if a True value is encountered, then check that
+            # all values after that row are also True.
+            null_entries_with_non_null_children = (
+                ~null_mask_filtered[:, col_idx] & null_mask_filtered[:, col_idx - 1]
             )
+            if nw.to_py_scalar(null_entries_with_non_null_children.any()):
+                row_idx = null_entries_with_non_null_children.to_list().index(True)
+                raise ValueError(
+                    "None entries cannot have not-None children",
+                    df_sorted.row(row_idx),
+                )
 
     fill_series = nw.new_series(
         name="fill_value",
@@ -1893,13 +1896,13 @@ def _check_dataframe_all_leaves(df: nw.DataFrame) -> None:
     )
 
     null_indices = set(null_indices_mask.arg_true().to_list())
-    for i, (current_row, next_row) in enumerate(
+    for col_idx, (current_row, next_row) in enumerate(
         zip(row_strings[:-1], row_strings[1:]), start=1
     ):
-        if (next_row in current_row) and (i in null_indices):
+        if (next_row in current_row) and (col_idx in null_indices):
             raise ValueError(
                 "Non-leaves rows are not permitted in the dataframe \n",
-                df_sorted.row(i),
+                df_sorted.row(col_idx),
                 "is not a leaf.",
             )